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Hearing threshold for white noise?

AnalogSteph

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So this one might get me the stupid question of the week award or something... but anyway: We all know hearing threshold curves, which are taken using narrow bandwidth tones AFAIK. What do they mean for minimum detectable white noise level though? How low typically is it? Are there any studies? I didn't find anything but that doesn't have to mean a whole lot.

By my reckoning the answer should be "lower than you might think" (maybe around 5 dB SPL with young / largely unmolested hearing?), but I can't prove it.
 

pkane

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So this one might get me the stupid question of the week award or something... but anyway: We all know hearing threshold curves, which are taken using narrow bandwidth tones AFAIK. What do they mean for minimum detectable white noise level though? How low typically is it? Are there any studies? I didn't find anything but that doesn't have to mean a whole lot.

By my reckoning the answer should be "lower than you might think" (maybe around 5 dB SPL with young / largely unmolested hearing?), but I can't prove it.

The closest I've seen is ITU-R 468 weighting that's used to create a filter to apply to audio content, similar to the A-weighting. A-weighting is based on a Fletcher-Munson equal loudness curve, derived using single tones. ITU-R 468 is derived using pink noise bursts. The curves below are flipped compared to the usual equal-loudness curve presentation (ISO 226 is an updated/corrected version of Fletcher-Munson):

1594692089826.png
 
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PaulD

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So this one might get me the stupid question of the week award or something... but anyway: We all know hearing threshold curves, which are taken using narrow bandwidth tones AFAIK. What do they mean for minimum detectable white noise level though? How low typically is it? Are there any studies? I didn't find anything but that doesn't have to mean a whole lot.

By my reckoning the answer should be "lower than you might think" (maybe around 5 dB SPL with young / largely unmolested hearing?), but I can't prove it.
It might even be lower than that, because 0dB SPL is defined as the threshold of hearing at 1KHz, and we are more sensitive in the 2-5KHz region due to the resonance of the ear canal. White noise has equal energy per frequency, so there is more energy in the higher frequencies. It is conceivable that the threshold of hearing for white noise is very low.

I was just looking at this article (https://pubmed.ncbi.nlm.nih.gov/1211738/), but I cannot find any reliable dB SPL measures.
 

pozz

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What bandwidth of noise centered at what frequency? Do you mean white noise covering the entire audible bandwidth?

The equal loudness curves apply anyway. The main reason noise is used in audiometric tests is to control excitation of criticial bands, test masking and frequency discrimination and so on. There's no special hearing mechanism for noise vs. single tones, although more perceptual phenomena are added to mix as the sound gets more complex (beats, roughness, stream separation).
 
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AnalogSteph

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What bandwidth of noise centered at what frequency? Do you mean white noise covering the entire audible bandwidth?
Exactly this.

I know real-life noise emissions can be rather non-flat (waveguide-mounted tweeters, anyone?), but let's start with plain ol' 20 kHz BW white noise. Say you have some rather flat, traditional passive speakers and a somewhat noisy amplifier.
 

pozz

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Do you mean what you can reasonably expect in your room?

You have noise/masking sources that are present in your room already: ventilation, traffic, mechanical vibrations from appliances, talking. The list goes on.

It's pretty common to have fairly high SPL in bass that you don't actively hear, sloping down to a few dBs in the most sensitive hearing region around 3kHz. So you'll hear really quiet stuff there. Noise in active speakers is in that range too, unfortunately. For example: https://www.audiosciencereview.com/...ntrol-1-pro-monitors-review.10811/post-303904
 
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AnalogSteph

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Julian Dunn (R.I.P.) to the rescue:
Fielder [11] has shown that white noise at 4dB SPL is just audible for people in either a home listening or professional monitoring environment, even with environmental noise levels of 50dB SPL. This compares with maximum sound levels between 105dB and 112dB SPL (corresponding to digital full scale) for listening levels in domestic or review situations [6]. Subtraction of the 4dB figure from the peak level figures implies a dynamic range requirement, for the listener, of from 101dB to 108dB.
[6] Stuart, J. Robert - `Estimating the Significance of Errors in Audio Systems', Preprint 3208, presented at the 91st AES Convention (October 1991).
[...]
[11] Fielder, Louis D. - `Dynamic-Range Requirement for Subjectively Noise-Free Reproduction of Music', J. Audio Eng. Soc., vol 30 No. 7/8, pp 504-510 (July/August 1982)
Why does it not surprise me that I should find the answer in a 1992 paper citing another from 1982 while sorting through my PDF archive? Good paper, too. Nothing new under the sun and all.
 

j_j

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Well, you analyze the white noise in terms of energy/ERB, and then compare that to the limits of unimpaired hearing.

You get, for white noise, somewhere in the region of 4dB SPL or so, which works out to a noise level in the most sensitive ERB (which varies depending on ear canal resonance), to just barely above the noise level of the atmosphere due to molecular noise.

Note, this depends not only on the spectrum noise, but also on the structure of the white noise to some extent. Some versions that call themselves "white noise" are not that good at having a consistent spectrum across time.
 
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