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St y fra talende personer p spisesteder

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St y fra talende personer p spisesteder

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    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

    9. Theoretical model – Noise level in room

    10. Noise level as a function of absorption area and number of speaking persons

    11. Noise level and speech level

    12. Theoretical model

    13. Example 1 Food court, Vol. = 7228 m3, RT = 1,3 s

    14. Example 2 Food court, Vol. = 3133 m3, RT = 0,9 s

    15. Example 3 Canteen, Vol. = 1235 m3, RT = 0,47 s

    16. Example 1 Food court, Vol. = 7228 m3, RT = 1,3 s

    17. Example 2 Food court, Vol. = 3133 m3, RT = 0,9 s

    18. Example 3 Canteen, Vol. = 1235 m3, RT = 0,47 s

    19. Needed absorption area per person

    20. Needed absorption area per person

    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

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