LETTERS TO THE EDITOR This Letters section is for publishing (a) brief acoustical research or applied acoustical reports, (b) comments on articles or letters previously published in this Journal, and (c) a reply by the article author to criticism by the Letter author in (b). Extensive reports should be submitted as articles, not in a letter series. Letters are peer-reviewed on the same basis as articles, but usually require less review time before acceptance. Letters cannot exceed four printed pages (approximately 3000–4000 words) including figures, tables, references, and a required abstract of about 100 words.
Differences in subjective loudness and annoyance depending on the road traffic noise spectrum (L) Antonio J. Torijaa) and Ian H. Flindell Institute of Sound and Vibration Research, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom
(Received 17 July 2013; revised 19 September 2013; accepted 25 November 2013) There is at present no consensus about the relative importance of low frequency content in urban road traffic noise. The hypothesis underlying this research is that changes to different parts of the spectrum will have different effects depending on which part of the spectrum is subjectively dominant in any particular situation. This letter reports a simple listening experiment which demonstrates this effect using typical urban main road traffic noise in which the low frequency content is physically dominant without necessarily being subjectively dominant. C 2014 Acoustical Society of America. [http://dx.doi.org/10.1121/1.4842456] V PACS number(s): 43.50.Qp, 43.50.Ba, 43.50.Rq [SF]
I. INTRODUCTION
Disturbance and annoyance caused by exposure to road traffic noise is widely considered as one of the major environmental problems in urban aglomerations.1,2 Noise annoyance is influenced by sound related factors and by person-related factors which can affect the perception of those sounds.1,3 Relevant acoustic features include the sound pressure level, the duration, and time pattern of exposure and the frequency spectrum.1 Differences in reported annoyance associated with different types of road-traffic vehicles4 have been explained to some extent by differences in spectral characteristics caused by different engine types and operating conditions.5 Several laboratory studies have shown that reported annoyance can be significantly influenced by frequency spectrum-related factors.6,7 On the other hand, experience shows that situation and context can affect which of the different acoustic features present has the greatest influence on reported annoyance. Listeners tend to focus their attention on different parts of the spectrum in different situations, depending on subjective dominance. Our hypothesis is that changes to different parts of the spectrum will have different effects depending on which part of the spectrum is subjectively dominant in any particular situation. Subjective dominance is not always simple to predict because it depends on selective attention in addition to the relative frequency weighting of the ear. For example, the relative amount of low frequency sound present will have different effects depending on the extent to which low frequencies are a)
Author to whom correspondence should be addressed. Electronic mail: [email protected]
J. Acoust. Soc. Am. 135 (1), January 2014
Pages: 1–4
subjectively dominant or not in any particular situation. This letter reports a simple listening experiment which demonstrates this effect using typical urban main road traffic noise in which the low frequency content is physically dominant without necessarily being subjectively dominant. The frequency content of road traffic noise is highly affected by its circulation dynamics, i.e., the particular ways in which vehicles are circulating in terms of speed, gear, engine rpm, tire-road interaction, and interaction with other vehicles. At low speeds, engine noise and low rpm are likely to dominate whereas at speeds exceeding 50 km/h rolling noise and higher rpm are more likely to dominate.8,9 Under the typical circulation dynamics in urban agglomerations, engine noise and rolling noise are the main contributors mainly contributing low and medium frequencies.9 Some researchers have pointed out low-frequency noise as one of the main contributors to noise annoyance.10,11 More12 reported a comprehensive study on low-frequency noise where both the importance of the low-frequency noise and a series of metrics for characterizing it, e.g., lowfrequency noise threshold curves and its conversion into low frequency loudness threshold curves, are presented and described. However, there is no consensus about the relative importance of the low-frequency content. Some studies suggest that road traffic sounds with significant low-frequency content are subjectively louder and more annoying.13,14 Other studies, such as Versfeld and Vos,6 suggest the opposite. Kim et al.5 observed that, in general, the higher frequencies appear to be more significant for annoyance. In addition, while it is well known that human hearing is less sensitive to low frequencies when heard separately than to mid and high frequencies at least at lower sound levels, it
0001-4966/2014/135(1)/1/4/$30.00
C 2014 Acoustical Society of America V
1
has not been established to what extent this observation translates to wide-band sounds.
TABLE I. A-weighted sound level (LAeq) of each of the reproduced experimental sound. LAeq
II. METHODS A. Participants
Thirty listeners (14 males and 16 females with 18–65 yr of age) participated with three listeners at a time rating each of 12 sounds (see below). All listeners passed an online hearing test and were paid a small thank you gift for taking part. B. Stimuli
A 15 s master recording of continuous urban main road traffic noise was selected as the basis for all sounds used in the listening tests. The original recording was made using a SQuadriga – Head Acoustics binaural stereo system. The recording mainly comprises continuous road traffic background noise with up to four individual vehicles being
Gain setting 9 dB 3 dB þ3 dB þ9 dB
LF
MF
HF
68.09 68.17 68.40 69.08
60.97 65.58 71.06 76.85
68.00 68.13 68.46 69.33
identifiable from time to time within the overall 15 s duration. The sound level at the recording position was relatively constant within a range of plus and minus 2–3 dB with no subjectively identifiable impulse sounds. The original sound level over the 15 s as measured outdoors was 70.3 LAeq. The original spectrum is shown in Fig. 1. The experimental sounds for the listening tests were produced by boosting or cutting the low frequency (LF), mid frequency (MF), or high frequency (HF) ranges as shown in Fig. 1. The low pass shelf filter cut-off frequency was 315 Hz with a 0.1 octave transition. The mid range band-pass or band-stop filter center frequency was 794 Hz with a 3 octave bandwidth. The high pass shelf filter cut-off frequency was 2000 Hz with a 0.1 octave transition. Each filter was applied with 9 dB, 3 dB, þ3 dB, and þ9 dB relative gain setting to produce the 12 filtered sounds shown in Fig. 1. The amplifier gain in the listening room was set so that the original unmodified recording would play back at 70.3 LAeq, and all the experimental sounds were then reproduced without changing the overall gain setting, i.e., the A-weighted sound level would have been increased or decreased to some extent depending on the filter settings (Table I). C. Apparatus
FIG. 1. Frequency spectra of the original road traffic sound and the 9 dB, 3 dB, þ3 dB, and þ9 dB filter gain settings for (a) LF, (b) MF, and (c) HF. 2
J. Acoust. Soc. Am., Vol. 135, No. 1, January 2014
The listening tests were all conducted in an anechoic chamber to simulate outdoor free field conditions. All audio signals (.wav files) were generated via a mainstream laptop with a good quality sound card, and then sent to the loudspeakers via a small high quality audio mixing console (Yamaha MG10/2). The stimuli were reproduced via two high-resolution loudspeakers (Behringer Truth model B2031A). Both the two loudspeakers and the three chairs for the participants were placed in the anechoic chamber so that the three participants received the same sound level, as measured at representative head height positions with no listeners present. The sound-level-meter (SLM) model Norsonic Environmental Analyzer type 121, with a Norsonic free-field microphone type 1225 was used. This SLM was calibrated to 94 dB/1000 Hz with a Sound Level Calibrator type 4230. The amplifier gain was checked before each listening session using a reference 80 dBA pink noise .wav file signal reproduced through the same system. Using a reference signal approximately 10 dB higher than the unmodified sound LAeq ensured sufficient headroom to avoid distortion for any of the frequency boosted sounds. A. J. Torija and I. H. Flindell: Letters to the Editor
TABLE III. Results (r2 and b values) of the Linear Regression analysis (N ¼ 40) for estimating perceived annoyance and perceived loudness from the filter gain setting in each frequency range.
r2 Standardized coefficient (b) r2 Standardized coefficient (b) r2 Standardized coefficient (b)
LF MF HF
a
Perceived loudness
Perceived annoyance
0.515 0.717a 0.715 0.846a 0.691 0.831a
0.241 0.491a 0.527 0.726a 0.713 0.844a
p 0.01.
III. RESULTS
FIG. 2. Average value (1-to-5 scale units) of listeners’ perception of (a) loudness and (b) annoyance with variations of 9 dB, 3 dB, þ3 dB, and þ9 dB in filter gain at LF, MF, and HF.
D. Procedure
The aims and procedures were carefully explained and listeners were then asked to sign the standard voluntary consent forms. Listeners were told that the sounds were recorded outdoors in a public open space alongside a busy main road in a city and that they should judge them in that context. Both reported loudness and annoyance were assessed using different versions of the standardized ISO/TS 1566615 specification for noise annoyance questionnaires. The five point semantic scale; “Not at all,” “Slightly,” “Moderately,” “Very,” and “Extremely,” was used throughout in addition to other questionnaire items addressed to related topics and issues. The order of presentation of the 12 filtered sounds within each of the 10 listening sessions was fully randomized and each group of 3 listeners was allowed 20 s to complete the questionnaires after listening to each sound sample.
Figures 2(a) and 2(b) show the relationships between reported loudness and reported annoyance and the filter settings for all three (LF, MF, and HF) frequency bands. Figure 2(a) shows similar increases in reported loudness with increases in filter setting for all three frequency bands. Figure 2(b) shows significant differences in the rates of increase in reported annoyance with increases in filter setting for the LF frequency band. Table II shows lower regression coefficients between average reported loudness and average reported annoyance for each group of 3 listeners for the LF frequency band than for the MF and HF frequency bands. Table III shows lower regression coefficients between average reported loudness for each group of three listeners and filter gain setting and between average reported annoyance for each group of three listeners and filter gain setting for the LF frequency band than for the MF and HF frequency bands. A subsequent analysis of variance (ANOVA) (Table IV) investigated statistical significance for the main effects described above. All F-ratio statistics were significant at better than p 0.01. The variances attributable to filter gain setting within each frequency band filter were considerably lower for the LF frequency band than for the MF and HF frequency bands. Our data suggest that for the filtered road traffic sounds tested, while reported loudness is affected to some extent by filter gain setting at all three frequency bands, reported TABLE IV. One-way ANOVA results (mean square and F-value) for testing the statistical significance of the effect of the filter gain setting in each frequency range on perceived loudness and perceived annoyance.
LF TABLE II. Results (r2 and F values) of the Linear Regression analysis (N ¼ 40) for estimating perceived annoyance from perceived loudness, for each frequency range.
r2 F a
LF
MF
HF
0.545 45.468a
0.718 96.648a
0.748 116.916a
p 0.01.
J. Acoust. Soc. Am., Vol. 135, No. 1, January 2014
MF
HF
a
Between group Within group F Between group Within group F Between group Within group F
Perceived loudness
Perceived annoyance
3.159 0.219 14.457a 4.830 0.153 31.510a 5.794 0.205 28.308a
1.271 0.235 5.397a 4.254 0.299 14.207a 5.450 0.179 30.511a
p 0.01. A. J. Torija and I. H. Flindell: Letters to the Editor
3
annoyance is dominated by the MF and HF frequency bands. Fidell et al.,16,17 Leventhal,18 and Huang et al.19 all found that the low frequency noise was relatively more important in explaining noise annoyance than in this study. Considering Nakamura and Tokita’s low frequency noise threshold curves20 it appears that the low frequency content in our study was less dominant (subjectively) than the mid and high frequency content, even for the LF boosted conditions. This does not of course mean that the LF content in urban traffic noise will always be less dominant than the MF and HF content, because there are many situations, such as indoor listening, where the LF content is relatively more prominent because of attenuation of MF and HF content through the building envelope. IV. CONCLUSIONS
A listening trial conducted to investigate the effect on reported loudness and reported annoyance of altering the frequency spectrum of recorded urban main road traffic sounds showed that changes in LF content were less significant for reported annoyance than equivalent changes in MF and HF content. This result is consistent with the assumption that, for the filtered road traffic sounds tested, the MF and HF content was subjectively dominant. Because of the importance that the knowledge of the relationship between the different spectral composition of road traffic noise and both reported loudness and reported annoyance, as well as the finding of the spectral regions subjectively dominant may have in understanding the perception of soundscapes in open public spaces, and in the design of actions for their sound improvement, this research has been carried out under outdoor conditions. However, further work will investigate the conditions under which LF content (or other often less important acoustic features) might be more significant for reported annoyance, and possibly even for reported loudness, in situations where other acoustic features such as MF and HF content are less dominant subjectively as for example under indoor conditions. The practical implication is that it is important to understand which acoustic features of any sound are subjectively dominant when designing noise control action so that these may be addressed first. ACKNOWLEDGMENTS
This work is funded by the University of Malaga and the European Commission under the Agreement Grant No. 246550 of the seventh Framework Programme for R & D of the EU, granted within the People Programme, «Co-funding
4
J. Acoust. Soc. Am., Vol. 135, No. 1, January 2014
of Regional, National and International Programmes» (COFUND). 1
B. Jakovljevic, K. Paunovic, and G. Belojevic, “Road-traffic noise and factors influencing noise annoyance in an urban population,” Environ. Int. 35, 552–556 (2009). 2 A. J. Torija, D. P. Ruiz, V. Alba-Fernandez, and A. Ramos-Ridao, “Noticed sound events management as a tool for inclusion in the action plans against noise in medium-sized cities,” Landscape Urban Plan. 104, 148–156 (2012). 3 D. Ouis, “Annoyance from road traffic noise: A review,” J. Environ. Psychol. 21, 101–120 (2001). 4 € E. Ohrstr€ om, M. Bj€ orkman, and R. Rylander, “Laboratory annoyance and different traffic noise sources,” J. Sound Vib. 70, 333–341 (1980). 5 J. Kim, C. Lim, J. Hong, and S. Lee, “Noise-induced annoyance from transportation noise: Short-term responses to a single noise source in a laboratory,” J. Acoust. Soc. Am. 127, 804–814 (2010). 6 N. J. Versfeld and J. Vos, “Annoyance caused by sounds of wheeled and tracked vehicle,” J. Acoust. Soc. Am. 101, 2677–2685 (1997). 7 A. J. Torija, D. P. Ruiz, B. De Coensel, D. Botteldooren, B. Berglund, and A. Ramos-Ridao, “Relationship between road and railway noise annoyance and overall indoor sound exposure,” Transport. Res. D-TR. E. 16, 15–22 (2011). 8 U. Sandberg and J. A. Ejsmont, Tyre/Road Noise (Informex Ejsmont and Sandberg Handelsbolag, Sweden, 2002), pp. 1–640. 9 A. J. Torija and D. P. Ruiz, “Using recorded sound spectral profile as input data for real-time short-term urban road-traffic-flow estimation,” Sci. Total Environ. 435–436, 270–279 (2012). 10 K. Persson, M. Bj€ orkman, and R. Rylander, “An experimental evaluation of annoyance due to low frequency noise,” J. Low Freq. Noise Vib. 4, 145–153 (1985). 11 H. G. Leventhall, “Low frequency noise and annoyance,” Noise Health 6, 59–72 (2004). 12 S. R. More, “Aircraft noise characteristics and metrics,” Report No. PARTNER-COE-2011-004, Cambridge, MA, USA, 2011. 13 G. R. Watts, “A comparison of noise measures for assessing vehicle noisiness,” J. Sound Vib. 180, 493–512 (1995). 14 M. E. Nilsson, “A-weighted sound pressure level as an indicator of shortterm loudness or annoyance of road-traffic sound,” J. Sound Vib. 302, 197–207 (2007). 15 ISO, Acoustics-Assessment of noise annoyance by means of social and socio-acoustic surveys, ISO/TS15666:2003(E) (ISO, Geneva, Switzerland, 2003). 16 S. Fidell, L. Silvati, K. Pearsons, S. Lind, and R. Howe, “Field study of the annoyance of low-frequency runway sideline noise,” J. Acoust. Soc. Am. 106, 1408–1415 (1999). 17 S. Fidell, K. Pearsons, L. Silvati, and M. Sneddon, “Relationship between low-frequency aircraft noise and annoyance due to rattle and vibration,” J. Acoust. Soc. Am. 111, 1743–1750 (2002). 18 G. Leventhall, “A review of published research on low frequency noise and its effects,” Report for Department for Environment, Food and Rural Affairs (DEFRA), May 2003. Available at http://archive.defra.gov.uk/environment/ quality/noise/research/lowfrequency/documents/lowfreqnoise.pdf. 19 Y. Huang, G. Di, Y. Zhu, Y. Hong, and B. Zhang, “Pair-wise comparison experiment on subjective annoyance rating of noise samples with different frequency spectrums but same A-weighted level,” Appl. Acoust. 69, 1205–1211 (2008). 20 S. Nakamura and Y. Tokita, “Frequency characteristics of subjective responses to low frequency sound,” in Proceedings of the Inter-Noise 1981, Amsterdam, The Netherlands (1981).
A. J. Torija and I. H. Flindell: Letters to the Editor
Copyright of Journal of the Acoustical Society of America is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
Differences in subjective loudness and annoyance depending on the road traffic noise spectrum (L) Antonio J. Torijaa) and Ian H. Flindell Institute of Sound and Vibration Research, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom
(Received 17 July 2013; revised 19 September 2013; accepted 25 November 2013) There is at present no consensus about the relative importance of low frequency content in urban road traffic noise. The hypothesis underlying this research is that changes to different parts of the spectrum will have different effects depending on which part of the spectrum is subjectively dominant in any particular situation. This letter reports a simple listening experiment which demonstrates this effect using typical urban main road traffic noise in which the low frequency content is physically dominant without necessarily being subjectively dominant. C 2014 Acoustical Society of America. [http://dx.doi.org/10.1121/1.4842456] V PACS number(s): 43.50.Qp, 43.50.Ba, 43.50.Rq [SF]
I. INTRODUCTION
Disturbance and annoyance caused by exposure to road traffic noise is widely considered as one of the major environmental problems in urban aglomerations.1,2 Noise annoyance is influenced by sound related factors and by person-related factors which can affect the perception of those sounds.1,3 Relevant acoustic features include the sound pressure level, the duration, and time pattern of exposure and the frequency spectrum.1 Differences in reported annoyance associated with different types of road-traffic vehicles4 have been explained to some extent by differences in spectral characteristics caused by different engine types and operating conditions.5 Several laboratory studies have shown that reported annoyance can be significantly influenced by frequency spectrum-related factors.6,7 On the other hand, experience shows that situation and context can affect which of the different acoustic features present has the greatest influence on reported annoyance. Listeners tend to focus their attention on different parts of the spectrum in different situations, depending on subjective dominance. Our hypothesis is that changes to different parts of the spectrum will have different effects depending on which part of the spectrum is subjectively dominant in any particular situation. Subjective dominance is not always simple to predict because it depends on selective attention in addition to the relative frequency weighting of the ear. For example, the relative amount of low frequency sound present will have different effects depending on the extent to which low frequencies are a)
Author to whom correspondence should be addressed. Electronic mail: [email protected]
J. Acoust. Soc. Am. 135 (1), January 2014
Pages: 1–4
subjectively dominant or not in any particular situation. This letter reports a simple listening experiment which demonstrates this effect using typical urban main road traffic noise in which the low frequency content is physically dominant without necessarily being subjectively dominant. The frequency content of road traffic noise is highly affected by its circulation dynamics, i.e., the particular ways in which vehicles are circulating in terms of speed, gear, engine rpm, tire-road interaction, and interaction with other vehicles. At low speeds, engine noise and low rpm are likely to dominate whereas at speeds exceeding 50 km/h rolling noise and higher rpm are more likely to dominate.8,9 Under the typical circulation dynamics in urban agglomerations, engine noise and rolling noise are the main contributors mainly contributing low and medium frequencies.9 Some researchers have pointed out low-frequency noise as one of the main contributors to noise annoyance.10,11 More12 reported a comprehensive study on low-frequency noise where both the importance of the low-frequency noise and a series of metrics for characterizing it, e.g., lowfrequency noise threshold curves and its conversion into low frequency loudness threshold curves, are presented and described. However, there is no consensus about the relative importance of the low-frequency content. Some studies suggest that road traffic sounds with significant low-frequency content are subjectively louder and more annoying.13,14 Other studies, such as Versfeld and Vos,6 suggest the opposite. Kim et al.5 observed that, in general, the higher frequencies appear to be more significant for annoyance. In addition, while it is well known that human hearing is less sensitive to low frequencies when heard separately than to mid and high frequencies at least at lower sound levels, it
0001-4966/2014/135(1)/1/4/$30.00
C 2014 Acoustical Society of America V
1
has not been established to what extent this observation translates to wide-band sounds.
TABLE I. A-weighted sound level (LAeq) of each of the reproduced experimental sound. LAeq
II. METHODS A. Participants
Thirty listeners (14 males and 16 females with 18–65 yr of age) participated with three listeners at a time rating each of 12 sounds (see below). All listeners passed an online hearing test and were paid a small thank you gift for taking part. B. Stimuli
A 15 s master recording of continuous urban main road traffic noise was selected as the basis for all sounds used in the listening tests. The original recording was made using a SQuadriga – Head Acoustics binaural stereo system. The recording mainly comprises continuous road traffic background noise with up to four individual vehicles being
Gain setting 9 dB 3 dB þ3 dB þ9 dB
LF
MF
HF
68.09 68.17 68.40 69.08
60.97 65.58 71.06 76.85
68.00 68.13 68.46 69.33
identifiable from time to time within the overall 15 s duration. The sound level at the recording position was relatively constant within a range of plus and minus 2–3 dB with no subjectively identifiable impulse sounds. The original sound level over the 15 s as measured outdoors was 70.3 LAeq. The original spectrum is shown in Fig. 1. The experimental sounds for the listening tests were produced by boosting or cutting the low frequency (LF), mid frequency (MF), or high frequency (HF) ranges as shown in Fig. 1. The low pass shelf filter cut-off frequency was 315 Hz with a 0.1 octave transition. The mid range band-pass or band-stop filter center frequency was 794 Hz with a 3 octave bandwidth. The high pass shelf filter cut-off frequency was 2000 Hz with a 0.1 octave transition. Each filter was applied with 9 dB, 3 dB, þ3 dB, and þ9 dB relative gain setting to produce the 12 filtered sounds shown in Fig. 1. The amplifier gain in the listening room was set so that the original unmodified recording would play back at 70.3 LAeq, and all the experimental sounds were then reproduced without changing the overall gain setting, i.e., the A-weighted sound level would have been increased or decreased to some extent depending on the filter settings (Table I). C. Apparatus
FIG. 1. Frequency spectra of the original road traffic sound and the 9 dB, 3 dB, þ3 dB, and þ9 dB filter gain settings for (a) LF, (b) MF, and (c) HF. 2
J. Acoust. Soc. Am., Vol. 135, No. 1, January 2014
The listening tests were all conducted in an anechoic chamber to simulate outdoor free field conditions. All audio signals (.wav files) were generated via a mainstream laptop with a good quality sound card, and then sent to the loudspeakers via a small high quality audio mixing console (Yamaha MG10/2). The stimuli were reproduced via two high-resolution loudspeakers (Behringer Truth model B2031A). Both the two loudspeakers and the three chairs for the participants were placed in the anechoic chamber so that the three participants received the same sound level, as measured at representative head height positions with no listeners present. The sound-level-meter (SLM) model Norsonic Environmental Analyzer type 121, with a Norsonic free-field microphone type 1225 was used. This SLM was calibrated to 94 dB/1000 Hz with a Sound Level Calibrator type 4230. The amplifier gain was checked before each listening session using a reference 80 dBA pink noise .wav file signal reproduced through the same system. Using a reference signal approximately 10 dB higher than the unmodified sound LAeq ensured sufficient headroom to avoid distortion for any of the frequency boosted sounds. A. J. Torija and I. H. Flindell: Letters to the Editor
TABLE III. Results (r2 and b values) of the Linear Regression analysis (N ¼ 40) for estimating perceived annoyance and perceived loudness from the filter gain setting in each frequency range.
r2 Standardized coefficient (b) r2 Standardized coefficient (b) r2 Standardized coefficient (b)
LF MF HF
a
Perceived loudness
Perceived annoyance
0.515 0.717a 0.715 0.846a 0.691 0.831a
0.241 0.491a 0.527 0.726a 0.713 0.844a
p 0.01.
III. RESULTS
FIG. 2. Average value (1-to-5 scale units) of listeners’ perception of (a) loudness and (b) annoyance with variations of 9 dB, 3 dB, þ3 dB, and þ9 dB in filter gain at LF, MF, and HF.
D. Procedure
The aims and procedures were carefully explained and listeners were then asked to sign the standard voluntary consent forms. Listeners were told that the sounds were recorded outdoors in a public open space alongside a busy main road in a city and that they should judge them in that context. Both reported loudness and annoyance were assessed using different versions of the standardized ISO/TS 1566615 specification for noise annoyance questionnaires. The five point semantic scale; “Not at all,” “Slightly,” “Moderately,” “Very,” and “Extremely,” was used throughout in addition to other questionnaire items addressed to related topics and issues. The order of presentation of the 12 filtered sounds within each of the 10 listening sessions was fully randomized and each group of 3 listeners was allowed 20 s to complete the questionnaires after listening to each sound sample.
Figures 2(a) and 2(b) show the relationships between reported loudness and reported annoyance and the filter settings for all three (LF, MF, and HF) frequency bands. Figure 2(a) shows similar increases in reported loudness with increases in filter setting for all three frequency bands. Figure 2(b) shows significant differences in the rates of increase in reported annoyance with increases in filter setting for the LF frequency band. Table II shows lower regression coefficients between average reported loudness and average reported annoyance for each group of 3 listeners for the LF frequency band than for the MF and HF frequency bands. Table III shows lower regression coefficients between average reported loudness for each group of three listeners and filter gain setting and between average reported annoyance for each group of three listeners and filter gain setting for the LF frequency band than for the MF and HF frequency bands. A subsequent analysis of variance (ANOVA) (Table IV) investigated statistical significance for the main effects described above. All F-ratio statistics were significant at better than p 0.01. The variances attributable to filter gain setting within each frequency band filter were considerably lower for the LF frequency band than for the MF and HF frequency bands. Our data suggest that for the filtered road traffic sounds tested, while reported loudness is affected to some extent by filter gain setting at all three frequency bands, reported TABLE IV. One-way ANOVA results (mean square and F-value) for testing the statistical significance of the effect of the filter gain setting in each frequency range on perceived loudness and perceived annoyance.
LF TABLE II. Results (r2 and F values) of the Linear Regression analysis (N ¼ 40) for estimating perceived annoyance from perceived loudness, for each frequency range.
r2 F a
LF
MF
HF
0.545 45.468a
0.718 96.648a
0.748 116.916a
p 0.01.
J. Acoust. Soc. Am., Vol. 135, No. 1, January 2014
MF
HF
a
Between group Within group F Between group Within group F Between group Within group F
Perceived loudness
Perceived annoyance
3.159 0.219 14.457a 4.830 0.153 31.510a 5.794 0.205 28.308a
1.271 0.235 5.397a 4.254 0.299 14.207a 5.450 0.179 30.511a
p 0.01. A. J. Torija and I. H. Flindell: Letters to the Editor
3
annoyance is dominated by the MF and HF frequency bands. Fidell et al.,16,17 Leventhal,18 and Huang et al.19 all found that the low frequency noise was relatively more important in explaining noise annoyance than in this study. Considering Nakamura and Tokita’s low frequency noise threshold curves20 it appears that the low frequency content in our study was less dominant (subjectively) than the mid and high frequency content, even for the LF boosted conditions. This does not of course mean that the LF content in urban traffic noise will always be less dominant than the MF and HF content, because there are many situations, such as indoor listening, where the LF content is relatively more prominent because of attenuation of MF and HF content through the building envelope. IV. CONCLUSIONS
A listening trial conducted to investigate the effect on reported loudness and reported annoyance of altering the frequency spectrum of recorded urban main road traffic sounds showed that changes in LF content were less significant for reported annoyance than equivalent changes in MF and HF content. This result is consistent with the assumption that, for the filtered road traffic sounds tested, the MF and HF content was subjectively dominant. Because of the importance that the knowledge of the relationship between the different spectral composition of road traffic noise and both reported loudness and reported annoyance, as well as the finding of the spectral regions subjectively dominant may have in understanding the perception of soundscapes in open public spaces, and in the design of actions for their sound improvement, this research has been carried out under outdoor conditions. However, further work will investigate the conditions under which LF content (or other often less important acoustic features) might be more significant for reported annoyance, and possibly even for reported loudness, in situations where other acoustic features such as MF and HF content are less dominant subjectively as for example under indoor conditions. The practical implication is that it is important to understand which acoustic features of any sound are subjectively dominant when designing noise control action so that these may be addressed first. ACKNOWLEDGMENTS
This work is funded by the University of Malaga and the European Commission under the Agreement Grant No. 246550 of the seventh Framework Programme for R & D of the EU, granted within the People Programme, «Co-funding
4
J. Acoust. Soc. Am., Vol. 135, No. 1, January 2014
of Regional, National and International Programmes» (COFUND). 1
B. Jakovljevic, K. Paunovic, and G. Belojevic, “Road-traffic noise and factors influencing noise annoyance in an urban population,” Environ. Int. 35, 552–556 (2009). 2 A. J. Torija, D. P. Ruiz, V. Alba-Fernandez, and A. Ramos-Ridao, “Noticed sound events management as a tool for inclusion in the action plans against noise in medium-sized cities,” Landscape Urban Plan. 104, 148–156 (2012). 3 D. Ouis, “Annoyance from road traffic noise: A review,” J. Environ. Psychol. 21, 101–120 (2001). 4 € E. Ohrstr€ om, M. Bj€ orkman, and R. Rylander, “Laboratory annoyance and different traffic noise sources,” J. Sound Vib. 70, 333–341 (1980). 5 J. Kim, C. Lim, J. Hong, and S. Lee, “Noise-induced annoyance from transportation noise: Short-term responses to a single noise source in a laboratory,” J. Acoust. Soc. Am. 127, 804–814 (2010). 6 N. J. Versfeld and J. Vos, “Annoyance caused by sounds of wheeled and tracked vehicle,” J. Acoust. Soc. Am. 101, 2677–2685 (1997). 7 A. J. Torija, D. P. Ruiz, B. De Coensel, D. Botteldooren, B. Berglund, and A. Ramos-Ridao, “Relationship between road and railway noise annoyance and overall indoor sound exposure,” Transport. Res. D-TR. E. 16, 15–22 (2011). 8 U. Sandberg and J. A. Ejsmont, Tyre/Road Noise (Informex Ejsmont and Sandberg Handelsbolag, Sweden, 2002), pp. 1–640. 9 A. J. Torija and D. P. Ruiz, “Using recorded sound spectral profile as input data for real-time short-term urban road-traffic-flow estimation,” Sci. Total Environ. 435–436, 270–279 (2012). 10 K. Persson, M. Bj€ orkman, and R. Rylander, “An experimental evaluation of annoyance due to low frequency noise,” J. Low Freq. Noise Vib. 4, 145–153 (1985). 11 H. G. Leventhall, “Low frequency noise and annoyance,” Noise Health 6, 59–72 (2004). 12 S. R. More, “Aircraft noise characteristics and metrics,” Report No. PARTNER-COE-2011-004, Cambridge, MA, USA, 2011. 13 G. R. Watts, “A comparison of noise measures for assessing vehicle noisiness,” J. Sound Vib. 180, 493–512 (1995). 14 M. E. Nilsson, “A-weighted sound pressure level as an indicator of shortterm loudness or annoyance of road-traffic sound,” J. Sound Vib. 302, 197–207 (2007). 15 ISO, Acoustics-Assessment of noise annoyance by means of social and socio-acoustic surveys, ISO/TS15666:2003(E) (ISO, Geneva, Switzerland, 2003). 16 S. Fidell, L. Silvati, K. Pearsons, S. Lind, and R. Howe, “Field study of the annoyance of low-frequency runway sideline noise,” J. Acoust. Soc. Am. 106, 1408–1415 (1999). 17 S. Fidell, K. Pearsons, L. Silvati, and M. Sneddon, “Relationship between low-frequency aircraft noise and annoyance due to rattle and vibration,” J. Acoust. Soc. Am. 111, 1743–1750 (2002). 18 G. Leventhall, “A review of published research on low frequency noise and its effects,” Report for Department for Environment, Food and Rural Affairs (DEFRA), May 2003. Available at http://archive.defra.gov.uk/environment/ quality/noise/research/lowfrequency/documents/lowfreqnoise.pdf. 19 Y. Huang, G. Di, Y. Zhu, Y. Hong, and B. Zhang, “Pair-wise comparison experiment on subjective annoyance rating of noise samples with different frequency spectrums but same A-weighted level,” Appl. Acoust. 69, 1205–1211 (2008). 20 S. Nakamura and Y. Tokita, “Frequency characteristics of subjective responses to low frequency sound,” in Proceedings of the Inter-Noise 1981, Amsterdam, The Netherlands (1981).
A. J. Torija and I. H. Flindell: Letters to the Editor
Copyright of Journal of the Acoustical Society of America is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
