Quietest place on earth
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walter
Well-known member
...and getting quieter outside the chamber with the re-orgs and layoffs....
Axelerator
Well-known member
in this room your ear-stereovilli will straight go to brownian movement.
not too nice i think
not too nice i think
I've been inside a couple anechoic chambers (Bozak, and Peavey).
Even my brief visits were uncomfortable.
JR
Even my brief visits were uncomfortable.
JR
Phrazemaster
Well-known member
Why?JohnRoberts said:
audiomixer
Well-known member
emrr said:
-20.6dB what? I love those precise terms.
on the topic of uncomfortable - too much absorption does make you very dizzy indeed. I remember my first visit in the ETH Zürich anechoic chamber - testing my first 'professional' PA speaker. The tweeter did not survive.... the impression of very low volume made me turn the knob way passed the power handling of that poor tweeter.
on an other occasion I had the chance to listen to a retreat room for large space office - think of a larger phone booth: too bad they had 100% absorption all over the surfaces.
by the way - anechoic does not really mean lowest noise by default....
- Michael
I can only speculate, but we are used to hearing sound reflections from the space around us that give us a sense of whether we are in a closet or a large auditorium, even with our eyes closed. In an anechoic chamber we only hear direct sounds, or a very low noise floor.Phrazemaster said:
I basically recall that my brief duration inside made me prefer to be outside the chamber. I've asked engineers and techs who spent far more time inside than I, and none told me they liked it, or stayed longer than they had to.
JR
dBSPL
0dBSPL is deemed the quietest humans can hear.
Interesting that brownian motion of air is at -23dB.
-20 would be 1% of the quietest thing you can hear.
0dBSPL is deemed the quietest humans can hear.
Interesting that brownian motion of air is at -23dB.
-20 would be 1% of the quietest thing you can hear.
Ask this guy...
https://www.youtube.com/watch?v=mXVGIb3bzHI
They are usually quiet to get a better dynamic range without the need of too high SPL to start the measurements. The strange thing in -20dB are the instruments used to get that kind of measurements, I can probably imagine how they insulate the room even further to get that close to the brownian noise but what about the jhonson's noise of the instruments used? There is not much of a point in doing -20dB SPL to use a Rode NT1A with 7dB SPL EIN, which is quite impressive within the mics we are used to.
Once in an audiometry I got to hear -5dB in 500Hz IIRC, of course for 4kHz wasn't that good... Still with the headphones on, inside the cabin, I could hear the traffic in the street.
JS
https://www.youtube.com/watch?v=mXVGIb3bzHI
They are usually quiet to get a better dynamic range without the need of too high SPL to start the measurements. The strange thing in -20dB are the instruments used to get that kind of measurements, I can probably imagine how they insulate the room even further to get that close to the brownian noise but what about the jhonson's noise of the instruments used? There is not much of a point in doing -20dB SPL to use a Rode NT1A with 7dB SPL EIN, which is quite impressive within the mics we are used to.
Once in an audiometry I got to hear -5dB in 500Hz IIRC, of course for 4kHz wasn't that good... Still with the headphones on, inside the cabin, I could hear the traffic in the street.
JS
spica
Well-known member
To expand on what Rochey stated in response to the question of "dB what?", it is dB(A) referenced to 20 uPa (micro Pascals) sound pressure level (aka SPL as Rochey stated).
I work for B&K and helped come up with the methodology for testing that chamber. It is very challenging to measure something that quiet.
Two of my colleagues are in the video: https://www.youtube.com/watch?v=Cyqc_4ixV80
I work for B&K and helped come up with the methodology for testing that chamber. It is very challenging to measure something that quiet.
Two of my colleagues are in the video: https://www.youtube.com/watch?v=Cyqc_4ixV80
spica said:
Great to have you here then... The first question I'd like to ask is why? (other than beating the world record) What things are benefited from being measured in a -20dBA SPL environment instead in one at -13dBA SPL?
There may be some, but the things I can think about are more in the scientific order and probably a bit apart from acoustics, or at least the acoustics we are used to.
The other thing, can you give us a hint at least how you measured that, as Brownian noise is closer other physical limitations are closer as well. I guess A weighting takes away quite a lot of it shaving away the LF, and the later you do the filtering the more stages it helps to filter, but for the acoustic part the reference is already weighted. I know you can't talk a lot but anything you are able to tell us would be very welcomed. Thanks!
JS
that new chamber has 12 feet of sand surrounding it and 3 feet of ground up rubber,
it only meets spec at about 4 in the morning,
Marcelo from Chameleon Labs, ME, USC
"I have been involved in the design and manufacturing of professional loudspeaker systems since 1988. Along the way I have founded two companies focused in this market segment and been awarded five US patents in the area of transducer technology and loudspeaker acoustics. Over the last six years, I have focused my energies primarily in the area of near-field and mid-field studio monitoring systems having been the Director of Engineering at Event Electronics.
I have held positions which have provided me experience in the areas of product development, industrial and mechanical design, acoustic and electronic engineering as well as manufacturing engineering and technologies. I have also worked within sales and marketing organizations and garnered experience that allowed me to successfully create sales and distribution channels for the two companies I started up.
Specialties:
Analogue and digital audio system development
Complex active loudspeaker system design
Acoustic measurement and testing
Transducer design
Manufacturing engineering systems and strategies
Test systems for automated transducer and electronics production lines
Experience
Owner
CHV Tech LLC
February 2014 – Present (1 year 10 months)
CHV Tech is a consulting and engineering company focused on the design, development and testing of acoustic and electronic audio products.
Director of Engineering
Event Electronics / Rode Microphones
2006 – 2014 (8 years)
Founder / President
KV2 Audio LLC
October 2002 – May 2006 (3 years 8 months)
Director of Transducer Development
Mackie Designs Inc.
1998 – 2002 (4 years)
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Fussion Audio Inc.
1997 – May 1998 (1 year)
Start up Professional Audio company acquired by Mackie Designs in 1998
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RCF North America LLC
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Bertagni Electronic Sound Transducers
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Bertagni Electronic Sound Transducers
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it only meets spec at about 4 in the morning,
Marcelo from Chameleon Labs, ME, USC
"I have been involved in the design and manufacturing of professional loudspeaker systems since 1988. Along the way I have founded two companies focused in this market segment and been awarded five US patents in the area of transducer technology and loudspeaker acoustics. Over the last six years, I have focused my energies primarily in the area of near-field and mid-field studio monitoring systems having been the Director of Engineering at Event Electronics.
I have held positions which have provided me experience in the areas of product development, industrial and mechanical design, acoustic and electronic engineering as well as manufacturing engineering and technologies. I have also worked within sales and marketing organizations and garnered experience that allowed me to successfully create sales and distribution channels for the two companies I started up.
Specialties:
Analogue and digital audio system development
Complex active loudspeaker system design
Acoustic measurement and testing
Transducer design
Manufacturing engineering systems and strategies
Test systems for automated transducer and electronics production lines
Experience
Owner
CHV Tech LLC
February 2014 – Present (1 year 10 months)
CHV Tech is a consulting and engineering company focused on the design, development and testing of acoustic and electronic audio products.
Director of Engineering
Event Electronics / Rode Microphones
2006 – 2014 (8 years)
Founder / President
KV2 Audio LLC
October 2002 – May 2006 (3 years 8 months)
Director of Transducer Development
Mackie Designs Inc.
1998 – 2002 (4 years)
Founder / President
Fussion Audio Inc.
1997 – May 1998 (1 year)
Start up Professional Audio company acquired by Mackie Designs in 1998
Vice President of Marketing
RCF North America LLC
January 1994 – September 1997 (3 years 9 months)
Vice President of Business Development
Bertagni Electronic Sound Transducers
February 1992 – January 1994 (2 years)
Mechanical Engineer
Bertagni Electronic Sound Transducers
April 1988 – February 1992 (3 years 11 months)
spica
Well-known member
I wasn't involved in the discussions with Microsoft regarding their exact reasons for wanting the quietest testing room in the world but I would imagine it is for two reasons:
1) To simply have the quietest room in the world. When you're a company as large as Microsoft (or, really, a company of any size), it is a powerful statement to say you have the best available environment in the world for the testing you are performing. If you want to be a serious/top player in your field, having the best equipment/environment to prove/test it is a good start.
2) It depends on what they want to measure. It is important to remember that you ALWAYS measure at least two things when making a measurement - even an electrical measurement. There is some level of background noise ALWAYS - whether that is ambient noise in a room, electrical noise in test equipment, etc. Sometimes it doesn't matter - ie, the thing you are trying to test (and information you are trying to extract from the test) are completely out of the noise floor of everything else and unaffected. For really low level acoustic measurements, like emitted electrical noise of a screen, power supply, component, etc, the background noise has to be very low (at least -10 dB from the level you are trying to measure - for a good measurement). Since many of those components (the quiet ones at least) may already be at or below 0dB (re:20 uPa) (quieter than we can hear in very quiet environments) the test environment must be at least -10 dB below that to make a very good measurement.
CJ makes a good point that the room (and any room) will not have a consistent noise floor. There is no such thing as "sound proof" (if you hear someone use that term, slap them) - we can only attenuate what is going on outside of the room. For Microsoft, that attenuation is so good that the room gets to -20 dB(A) ambient background noise... when it is quiet around that room. During a work day with very loud things going on, perhaps the room is -15 dB(A) or ? By making the room VERY quiet (ie the attenuation is VERY good), you can be assured that at any time of the day/year/whatever that your measurements are still valid because who cares what is going on outside - the attenuation into the room is just that good. You shouldn't assume that, of course, but having a really good room is a very good starting point.
You might argue what is the point of measuring a component that measures -10 dB(A)... and you might have a point if that is the only thing in the system. However, when you have 100 of those components they would total +10 dB(A) (assuming they are incoherent to each other) and you might start to have something that is audible depending on its frequency range ( and any other noise present). If there are tonal components to the sound, you may have an actual sound quality "problem" on your hands.
The technique for measuring the room isn't really that complicated. The real problem with the measurement is that the room is below the noise floor of our quietest microphone. Therefore, a single microphone will not do. If you measure with two microphones, they will both have a noise floor that is incoherent (ie not related to each other). If the microphones are both measuring VERY close to the same point in space, they will be measuring the same signal from the room and it will be in phase between the two microphones. If you look at the coherent power between the two, you can very effectively remove the electrical noise because that is incoherent.
1) To simply have the quietest room in the world. When you're a company as large as Microsoft (or, really, a company of any size), it is a powerful statement to say you have the best available environment in the world for the testing you are performing. If you want to be a serious/top player in your field, having the best equipment/environment to prove/test it is a good start.
2) It depends on what they want to measure. It is important to remember that you ALWAYS measure at least two things when making a measurement - even an electrical measurement. There is some level of background noise ALWAYS - whether that is ambient noise in a room, electrical noise in test equipment, etc. Sometimes it doesn't matter - ie, the thing you are trying to test (and information you are trying to extract from the test) are completely out of the noise floor of everything else and unaffected. For really low level acoustic measurements, like emitted electrical noise of a screen, power supply, component, etc, the background noise has to be very low (at least -10 dB from the level you are trying to measure - for a good measurement). Since many of those components (the quiet ones at least) may already be at or below 0dB (re:20 uPa) (quieter than we can hear in very quiet environments) the test environment must be at least -10 dB below that to make a very good measurement.
CJ makes a good point that the room (and any room) will not have a consistent noise floor. There is no such thing as "sound proof" (if you hear someone use that term, slap them) - we can only attenuate what is going on outside of the room. For Microsoft, that attenuation is so good that the room gets to -20 dB(A) ambient background noise... when it is quiet around that room. During a work day with very loud things going on, perhaps the room is -15 dB(A) or ? By making the room VERY quiet (ie the attenuation is VERY good), you can be assured that at any time of the day/year/whatever that your measurements are still valid because who cares what is going on outside - the attenuation into the room is just that good. You shouldn't assume that, of course, but having a really good room is a very good starting point.
You might argue what is the point of measuring a component that measures -10 dB(A)... and you might have a point if that is the only thing in the system. However, when you have 100 of those components they would total +10 dB(A) (assuming they are incoherent to each other) and you might start to have something that is audible depending on its frequency range ( and any other noise present). If there are tonal components to the sound, you may have an actual sound quality "problem" on your hands.
The technique for measuring the room isn't really that complicated. The real problem with the measurement is that the room is below the noise floor of our quietest microphone. Therefore, a single microphone will not do. If you measure with two microphones, they will both have a noise floor that is incoherent (ie not related to each other). If the microphones are both measuring VERY close to the same point in space, they will be measuring the same signal from the room and it will be in phase between the two microphones. If you look at the coherent power between the two, you can very effectively remove the electrical noise because that is incoherent.
Thanks for all that.
I did knew about the 10dB rule for a measurement, I didn't imagine someone trying to measure something at -10dB(A). For the component measurement I guess I'd go for measuring 100 at the same time, but I get the point. Someone forgot to do their homework a few years ago with those inductors inside graphics cards, I guess is a known case.
Thanks again.
JS
I did knew about the 10dB rule for a measurement, I didn't imagine someone trying to measure something at -10dB(A). For the component measurement I guess I'd go for measuring 100 at the same time, but I get the point. Someone forgot to do their homework a few years ago with those inductors inside graphics cards, I guess is a known case.
Thanks again.
JS
spica
Well-known member
No problem. I'm just speculating. Sometimes you want to measure individual components to verify that no single one is a problem child. You probably wouldn't measure VERY quiet components at the component level though. At least not on a regular basis.
Measuring something that is -10 dB(A) probably isn't going to be common for MS... but maybe measuring stuff that gets to 0 dB(A). At least they'd like to be able to. In that case, knowing the room isn't contributing to the measurement during "loud" portions of the work day would be useful.
Their room goes to 11... in terms of attenuation. (That joke doesn't really apply but, if you're talking about obscure and somewhat absurd things, you might as well try to make a Spinal Tap reference. )
Measuring something that is -10 dB(A) probably isn't going to be common for MS... but maybe measuring stuff that gets to 0 dB(A). At least they'd like to be able to. In that case, knowing the room isn't contributing to the measurement during "loud" portions of the work day would be useful.
Their room goes to 11... in terms of attenuation. (That joke doesn't really apply but, if you're talking about obscure and somewhat absurd things, you might as well try to make a Spinal Tap reference. )
Not sure who they are trying to impress or if there is a real need.spica said:
That is a rule of thumb regarding relative contribution for incoherent sources (square root of sum of the squares, -10dB results in roughly 10% error). You can parse out measurements without that much noise floor but lose resolution/accuracy.
Unless they are designing measurement microphones I can't guess what they're up to, and can't imagine them pursuing that. In one of my dad's old acoustics text books there was a reference to a unit of absorption described as an open window of unit area.
(like I said a very old book). It is perhaps ironic that Microsoft known as a computer software company is building a modern physical anechoic chamber. Computer technology has all but obsoleted the need for "anechoic" measurements these days (using time windowing).
I am very curious about what they are up to, I am not aware of them working with exotic low noise semiconductors, or transducer hardware. A quiet box is different (simpler) than an anechoic chamber.
Curiouser and curiouser. Maybe the guy who replaced Balmer demanded a (very) quiet space.... 8)
JR
Gene Pink
Well-known member
JohnRoberts said:
Perhaps they are trying to hear the cheers and applause for Windows 8.
Gene
meditation room for Bill G
Goodizzy
Active member
This sounds like it could be used to test noise levels in extremely sensitive acoustic environments, like submarines.
It's likely a defense inititiative, as Microsoft doesn't just write software for the commercial and personal markets.
It's likely a defense inititiative, as Microsoft doesn't just write software for the commercial and personal markets.
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