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 The Effectof Humidity on Room Acoustics

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Sonic.beaver



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Join date : 2009-09-18

PostSubject: The Effectof Humidity on Room Acoustics   Wed Feb 01, 2012 6:08 am


Hi Zonees

Sonic test rooms with a "BOO!" test, sometimes with a small Chinese hand drum. I listen for the plosives/transients and listen in particular for the reverb tail.

I have observed when testing my room in this way that with a lower humidity -- 37 to 40% -- I hear tight transients and a controlled decay: BOO! and THonk! Music played back is controlled and clean.

As the humidity rises, things get muddy and the overhang increases noticeably. At 70% humidity, the effect is "BOOwooo....!" and "tThonk-k" and reproduced sound is muddier.

This effect of humidity on the acoustics of a room and the performance of the acoustic treatment is not unknown. It was discussed as far back as in 1931 –“The Effect of Humidity upon Absorption of Sound in a Room” Vern O Knudsen, J Acoust. Soc. Am. Vol 3 Issue 1A. The BBC also had a paper on this. Only thing is Knudsen and BBC observe and discuss the effect from 1KHz and 4 KHz and up respectively while to Sonic’s ears the effect starts at 500 hz or lower.

This isn’t something discussed at all in the hi-end magazines.

Michael -- your views?

Sonic
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Michael Green
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PostSubject: Re: The Effectof Humidity on Room Acoustics   Thu Feb 02, 2012 7:42 am

This is one of the missing chapters of high end as well one of the biggest effects on sound.

The magazines are here to sell ads and their client's products. Personally I haven't seen any of these guys go deep into the art of listening to the air itself. When they do come around to the "whole" of the tune ears will turn. The jump from a high humidity system to a low one is huge beyond belief until we live in it. And live in it is the key in my book. I can not recommend high enough having a low humidity setup. Everything including the sound waves respond with far more impact, pace, rhythm and dynamics. So much so that when I visit a high humidity system I know right off the top that it will be a trading game instead of a huge leaping sonic adventure.

The key ingredient to our listening in general is air. Once this air is filled with moisture the waves and electronic charges take on a new performance level all together. The addition of water vapor to air (making the air humid) reduces the density of the air, which may at first appear counter-intuitive.

This occurs because the molecular mass of water is less than the molecular mass of dry air. For any gas, at a given temperature and pressure, the number of molecules present is constant for a particular volume. So when water molecules are added to a given volume of air, the dry air molecules must decrease by the same number, to keep the pressure or temperature from increasing. Hence the mass per unit volume of the gas (its density) decreases. The results sonically are big enough to take a system from fast clean and vibrant, to slow muddy and lifeless.

For myself, I like listening to a system that is very dry. Not only does the air and pressure zones sound much better, but the equipment's performance takes a big jump as well. In dry air I hear changes across the whole range and the sound stage size is something to behold.


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Robert Harrison



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Join date : 2010-03-08
Location : Harwood Heights, Illinois

PostSubject: Re: The Effectof Humidity on Room Acoustics   Tue Feb 07, 2012 3:26 pm

Hey, Sonic,

Did I get my wires crossed or are you located in the Phillipines?

The movie theater I work at has been rented out several times over the years to show Filipino movies, currently one every month, for local Tagalog speaking Filipino audiences (no English subtitles). The soundtracks are Dolby Stereo SR noise reduction encoded, but I always wind up playing them back in mono with the Academy filter, which rolls off highs starting at 8,000hz. If I play them in SR stereo, they are screechy as hell.

So, today's question is: are these just bad mixes or do they sound perfectly normal in a Filipino theater because of the difference in humidity there? Because in the midwestern United States, as I said, the dialog is horribly screechy.

Robert
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Sonic.beaver



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PostSubject: Re: The Effectof Humidity on Room Acoustics   Wed Feb 08, 2012 11:14 am


Hi Robert

Sonic isn't located in the Philippines. But am in the same part of the world and subject to a constantly high humidity year round. I don't know which is more problematic -- 65 to 85% all year or like some places of the US where seasonal variations go from 35 to 80%.

I hear that the summer dog days can be hard on fine Martins, Gibsons and Santa Cruzes even with air conditioning. In the high humidity over here my Taylor and old Yamaha beater stay reliable and constant.

Sonic
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