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Re: Reference for typical SNRs is public spaces

Hi Andy.


This is a very tricky question. I am not aware of any definitive data that really

addresses the issue adequately.


Laboratory studies tend to use single sound sources in anechoic conditions.

The auditory system copes very well in these conditions. The results indicate

that listeners can cope with very low SNRs (e.g. -10 dB for spatialised speech-

shaped noise interference, and lower for speech interferers). Moreover, some

studies have used several interferers (e.g. Peissig and Kollmeier '97, Hawley et al.

'04), and shown a gradual elevation in SRT with increasing numbers of interferers.

Simulating a more complex scene, like a restaurant with multiple interferers

and reverberation produces progressive degradation, though. We have been

simulating up to eight interfering voices from a variety of speakers with reverb

based on real-room binaural room impulse responses. SRTs are around -2 to -3

dB with eigth interfering voices. I haven't begun to write this work up yet, but

the results are not disimilar to those from a cruder preliminary study published



Culling, J. F. (2013). “Energetic and informational masking in a simulated restaurant environment” in Moore, B. C. J., Carlyon, R. P., and Gockel, H., Patterson, R. D. and Winter, I. M.. (eds) Basic Aspects of Hearing: Physiology and Perception (Springer, New York)


There remain limitations to this approach, of course. The technique remains

dependent on standard target speech materials (IEEE/Harvard sentences)

that are not very typical of normal conversation - particularly lacking a

conversational context. It is also unclear whether 50% keyword intelligibility

is a tolerable level of comprehension for conversation.


Karolina's study has other limitations. If I remember correctly, the material

was recorded from hearing impaired individuals, who may avoid the more

severe listening conditions into which normally hearing people thrust

themselves. Also, the method of establishing the SNR from the recordings

would probably become impossible below a certain SNR, as it relies on

a researcher judging from the recordings alone whether or not target

speech is present. Noise level is collected from epochs without target

speech, and speech level is derived by subtraction.


Nonetheless, both approaches indicate that real-world SNRs are unlikely

to be very near -10 dB, but be somewhere around 0 dB. Karolina's work

suggests a bit above, mine a bit below.


I guess what is really needed is for pairs of interlocutors to be wired up with

close microphones at the mouth (to establish reliably who is talking when)

and at their ears, and then to go out for the night and try to produce normal

speaking and listening behaviour. Perhaps after a few nights of this they

would habituate to all the kit, and produce data that will get us closer to a

true answer.




From: AUDITORY - Research in Auditory Perception [mailto:AUDITORY@xxxxxxxxxxxxxxx] On Behalf Of Andy Sabin
Sent: 22 January 2014 17:53
To: AUDITORY@xxxxxxxxxxxxxxx
Subject: Reference for typical SNRs is public spaces


Hi List, 


Can anyone point me to a reference showing SNRs that are typically observed in public spaces (e.g., restaurants, bars ...etc)? I can find this info for overall SPL, but am having a hard time finding it for SNR. 



Andy Sabin