1 / 22

Støy fra talende personer på spisesteder

Støy fra talende personer på spisesteder. Jens Holger Rindel NAS Høstmøte, 16-17 oktober 2009 Trondheim. Noise from speaking persons in eating establishments. Jens Holger Rindel NAS Autumn Meeting, 16-17 October 2009 Trondheim. Outline. Speech level in noise, the Lombard effect

fauve
Download Presentation

Støy fra talende personer på spisesteder

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Støy fra talende personer på spisesteder Jens Holger Rindel NAS Høstmøte, 16-17 oktober 2009 Trondheim

  2. Noise from speaking persons in eating establishments Jens Holger Rindel NAS Autumn Meeting, 16-17 October 2009 Trondheim

  3. Outline Speech level in noise, the Lombard effect Theory - A prediction model Verification examples Recommendations Conclusion

  4. Speech level in noise • When many people are talking at the same time in a social gathering, typically in a reverberant room, it is a common experience that it can be very noisy • Restaurants and canteens are typical examples of rooms where noise from speech can be a problem • However, until now very little is known about the influence of the reverberation time on this kind of noise

  5. The Lombard effect • People adjust the speech level according to the ambient noise level (found by Lombard 1911) • The effect can be quantified by the parameter c • c is the speech level rise due to increased ambient noise (dB/dB) • Values of c in the range 0,5 – 0,7 dB/dB have been suggested in the literature

  6. Description of speech levels(Lazarus, 1986)

  7. Collected results LSA re LNA (Lazarus, 1986)

  8. Theoretical model – Sound power of speech Lazarus concluded that the Lombard effect starts at a ambient noise level of 45 dB(A) and a speech level of 55 dB(A) Relation between SPL and sound power level in a free field, distance r , directivity factor Q Assuming distance r = 1 m, directivity factor Q = 2 for speaking person, we get:

  9. Theoretical model – Noise level in room Assuming a diffuse sound field and equivalent absorption area A, the sound pressure level of the noise from NS speaking persons is: Insertion of the previous equations yields: where c is the speech level rise due to increased noise (dB/dB) A / NS is the absorption area per speaking person (m2)

  10. Noise level as a function of absorption area and number of speaking persons Parameter c (dB/dB)

  11. Noise level and speech level Parameter c = 0,5 dB/dB

  12. Theoretical model Insertion of reverberation time without people T0 (s), volume V (m3), absorption per person a, and total number of persons N: Final model for noise from speech: where g = N / NS

  13. Example 1Food court, Vol. = 7228 m3, RT = 1,3 s Parameter: g Number of persons per speaking person Ref.: Navarro & Pimentel (2007), Applied Acoustics 68, pp. 364-375

  14. Example 2Food court, Vol. = 3133 m3, RT = 0,9 s Parameter: g Number of persons per speaking person Ref.: Navarro & Pimentel (2007), Applied Acoustics 68, pp. 364-375

  15. Example 3Canteen, Vol. = 1235 m3, RT = 0,47 s Parameter: g Number of persons per speaking person Measurement A: First half of lunch break Measurement B: Second half of lunch break Ref.: Tang et al. (1997), JASA 101, pp. 2990-2993

  16. Example 1Food court, Vol. = 7228 m3, RT = 1,3 s g = 3 persons per speaking person Ref.: Navarro & Pimentel (2007), Applied Acoustics 68, pp. 364-375

  17. Example 2Food court, Vol. = 3133 m3, RT = 0,9 s g = 3 persons per speaking person Ref.: Navarro & Pimentel (2007), Applied Acoustics 68, pp. 364-375

  18. Example 3Canteen, Vol. = 1235 m3, RT = 0,47 s Measurement A: First half of lunch Measurement B: Second half of lunch g = 3 persons per speaking person Ref.: Tang et al. (1997), JASA 101, pp. 2990-2993

  19. Needed absorption area per person Speech effort Relaxed Normal Raised Loud Absorption area per person (m2) Noise level, LNA (dBA)

  20. Needed absorption area per person Speech effort Relaxed Normal Raised Loud 26 m2 7 m2 Absorption area per person (m2) 2 m2 Noise level, LNA (dBA)

  21. Recommendations With less than 2 m2 absorption per person the noise level may exceed 79 dBA and the speech effort is loud or shouting With 2 - 7 m2 absorption per person the noise level may be in the range 67 – 78 dBA and the speech effort is raised 7 m2 absorption per person is needed to obtain a noise level below 67 dBA and a speech effort of normal 26 m2 absorption per person is needed to obtain a noise level below 55 dBA and a speech effort of relaxed

  22. Conclusion • The noise level due to speech may be reduced by 6 dB if the reverberation time is halved • not by 3 dB as for ordinary noise sources • This is due to the Lombard effect, which can be quantified by the rate c = 0,5 dB/dB in the cases of eating establishments studied here • c is the speech level rise due to increased ambient noise • The major uncertainty is due to the arousal level of the gathered people, here expressed by the parameter g • g : Number of persons per speaking person • g = 3 was found to give the best agreement in most cases studied here

More Related