Listening Space Dynamic Range

amirm

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Apr 2, 2010
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One of the common arguments in audio circles is how much resolution we need for audio samples. The number of bits determines the dynamic range. So if we determine the dynamic range, we can work backward and arrive at the equiv. bits of resolution. Folks then quickly pull out their SPL meter, show pretty high meter readings of noise floor in recording/listening space, and declare that the required dynamic range is very low, much lower than even 16 bits requires. Therefore, even CD is a waste let alone high-resolution formats! At face value this seems rather valid. But when you dig deep, really deep, the story unravels as I told in Widescreen Review magazine article a few months ago. Since some time has past since its publication, I have gone ahead and put a copy online: Understanding True Room Dynamic Range: http://www.madronadigital.com/Library/RoomDynamicRange.html

The article also starts us on the path of understanding psychoacoustics, i.e. the science of how we hear, as applied to unusual situations such as room acoustics (the common place is in audio compression such as MP3/AAC).

Enjoy and as always, appreciate feedback/correction, etc. :)
 

DonH50

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Jun 22, 2010
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I will try to read it later, Amir. I am sure it's great. I will note in passing that we can pull signals from below the noise floor pretty readily as we can integrate out the noise and retain the signal. besides, any mother (or dad who's been around a mother) can tell you humans can pull a baby's cry out of the loudest party/movie even from another room/floor... :)
 

amirm

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Indeed that is true. Fielder, whose work I draw from, actually analyzes that. He outlines even more fascinating things. One example is this:

'In this paper, it is claimed that the ear is able to use spatial clues to hear noise levels from a single source 10 dB below room noise which originates from all directions."

This says that we hear noise from a speaker at a specific location (single source) that is a whopping 10 db lower than the room noise (from all directions)! In other words, the room noise does not determine the floor of our dynamic range that way.

I worried about losing people with this level of detail so did not quite go there :).
 

GaryProtein

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Jul 25, 2012
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Indeed that is true. Fielder, whose work I draw from, actually analyzes that. He outlines even more fascinating things. One example is this:

'In this paper, it is claimed that the ear is able to use spatial clues to hear noise levels from a single source 10 dB below room noise which originates from all directions."

This says that we hear noise from a speaker at a specific location (single source) that is a whopping 10 db lower than the room noise (from all directions)! In other words, the room noise does not determine the floor of our dynamic range that way.

I worried about losing people with this level of detail so did not quite go there :).

That is also why we could always hear program material that is lower in volume than the rumble level (do they still call it that?) on a turntable.
 

DonH50

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Jun 22, 2010
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Anything that is correlated can be pulled out from below the noise floor with enough averaging/filter (which our ear/brain do perform). Rumble is also deterministic, however, so it is like having a strong signal (though still weak) in the presence of a weak(er) signal. I do not know for sure, but would expect masking to come into play for signals that are very near the rumble frequency.

Note in the midrange 10 dB down is 1/2 the perceived loudness.
 

mojave

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Oct 29, 2010
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Nice article, Amir. I was just wondering this past weekend why I can hear my projector on low fan speed when it should be much quieter than my noise floor in my room.

The second sentence here needs a correction. Changing it to "may include" reads better.

Likewise, penetrations can occur in reverse direction and let external sound into the room. What might be there include freeway vibrations from miles away!
 

amirm

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Apr 2, 2010
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Thanks for the kind words on the article mojave and the correction! I just put it in there.

In a few weeks I will post the next one that is in the current issue of WSR and deals with psychoacoustics of first reflections in rooms. It is a much deeper dive than this one and hopefully has more useful advice :).
 

jkeny

Industry Expert, Member Sponsor
Feb 9, 2012
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Amir, great to see these articles will now get an airing on WBF. Looking forward to the comments on the second article, "It's not Simple" which, as you say, has a lot more meat on the bones of this first article. Well done!
 

amirm

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Apr 2, 2010
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Seattle, WA
Thanks for the kind words :). The next is definitely a much more meaningful peace. I have already written the article after that for WSR so once that comes out, I will put the "It's not simple" online. Shouldn't be long.
 

JonFo

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Jun 11, 2010
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Amir, Great article and well illustrated.

One correction: while I would agree that 12 to 14 bits is 'chicken $hit resolution', this phrase "... to poultry 12 to 14 bits." probably meant to read "... to a paltry 12 to 14 bits."
 

jkeny

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Haha, "chicken $hit" & "poultry 12 to 14 bits" - funny slip-up :)
 

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