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radulescu_paul_mircea

Acoustics Studies

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I want first to know what is the audible spectrum of humans, ear and other senses.

I cannot find any new study where they test the auditory system capacity , to get rid of 20-20k Hz , to make a difference where the cochlea stops functioning and other sesory inputs tend to be more important in the perception of those frequencies.

I have a professor that states the ear stops functioning at 200 hz hand hands over to other sensory inputs.

I know he is not right but I have to proove him so if you know of studies please link them here.

Paul

Edited:

This is what I found up to now

http://oto2.wustl.edu/cochlea/romesalt.pdf

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Here is a very interesting survey of the perception of infrasonic frequencies: Hearing at low and infrasonic frequencies

 

Yes, people do hear below 20 Hz, well below 20 Hz, and yes, hearing is the operative word, not tactile skin body sensations. 

 

One other article I will link to later (I have to run right now), a study that suggests that, despite bass aficionado claims, bass can actually contribute to hearing loss. 

 

EDIT: here is the article on how low frequency sound can damage your hearing. Bass enthusiasts always thought that bass was harmless, and, while it may not be as harmful as frequencies we are most sensitive too, it turns out not to be true that it has no effect on your long term hearing. 

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Wow!  Great article.  This appears to confirm that movie content below 10 Hz can still be heard.  However, It may not happen often on a system running flat at reference, in part due to masking effects.  it's also interesting that vibrotactile sensation has been observed to kick in at about 20 dB above the hearing threshold even for the lowest stuff.  This explains why ULF is mostly a boring affair on floors that don't resonate.  It won't be felt, even though it can still possibly be heard.

 

And for those who are chasing sound intensity / particle velocity as a means toward better tactile response:  experimental evidence (down to 25 Hz) that pressure is all that matters for bass, at least for hearing thresholds.  I guess there's no direct evidence here showing lack of difference in vibrotactile sensation, but I doubt the situation changes.

 

The second article posted on low frequency sound and hearing damage was pretty sparse on information.  The link to the actual paper was bad, and I had to track it down manually.  Here it is.  I would not call this light reading, and I admit it's not one of my disciplines and is pretty far over my head.  An interesting tidbit is that the tests used 90 seconds of 30 Hz sine wave at 120 dB.  I'm not surprised that they observed evidence for temporary changes in hearing that lasted for some time after the signal ("more than 100 s" in this case).  Either way, it appears to be a long way away from demonstrating a propensity for such sound to cause hearing damage.  That's not to say that people shouldn't play it safe and enjoy their bass with some moderation.

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As I recall, the original study saw temporary threshold shifts for exposure to loud bass. The type of threshold shifts that they saw makes it easier for upper frequency sound to cause permanent threshold shifts. The researchers also speculated in the conclusion that exposure to loud bass may also be able to cause permanent threshold shifts in its own. The takeaway for me is that loud bass is not as harmless as some bass heads have claimed in the past. 

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Because I have the job to check sound systems in different venues, I often check the subwoofers at high volume to see if there are any problems. Most of the times I use protection, sometimes even earplugs and headphones on top, but there are times when I forget some of my equipment and i have to do it without protection. I can tell you for sure one can have really big problems with his hearing after checking a stack of  4 double 21" subs, flat to 26 hz, for a few minutes. even with my ears covered with my hands, sometimes I feel my ears hurt and hurting is never a good sign. So yes, bass can damage your hearing!

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Something new and cool about room acoustics simulations.

“This paper will present and discuss diffusion and the many problems with trying to measure it, displaying the data and using this data in ways that allow us to better predict room responses. We will quickly discuss prior standards, their strengths and weaknesses and how a new proposed ASTM standard will correct those weaknesses. We will show that methods used in other areas of acoustics and electro-acoustics can be used to measure diffusion and display it in ways that allow directivity, magnitude, and phase to be displayed. These data sets can then be used in simulation programs, such as EASE. Odeon and CATT Acoustics, to better predict room responses for use in the design of rooms. We will present examples of those uses and the advantages in these proposals."

From ProSoundNetwork

 

https://acousticsfirst.info/2016/11/18/acoustics-first-makes-sound-visible/

 

http://www.acousticsfirst.com

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That is really cool stuff, thanks for sharing! I'm not sure if you are interested, but THE classic text on audiology can be read here: On the Sensations of Tone by Helmholtz. A few of the pages are a bit garbled but it is very interesting to look through nonetheless. 

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I'm not an EE or an amp specialist, so it'd take a lot of time for me to make sense of what they were proposing in that paper.  From what it looks like though the concept requires the amp electronics and speaker transducers to be designed together simultaneously.  This considerably limits flexibility, and while it may simplify the overall design, it may complicate the *design process*.  Why?  Because the designers would have to have strong knowledge of both amplifier electronics and electro-acoustic transducers.  Most engineers are more specialized than that.  Another issue is that the transducers may not behave as linearly as electrical components in an amp would, which could complicate things quite a bit.

Also, it's not obvious to me that this tighter design integration would really solve any problems.  For example, one supposed advantage of the integrated approach is that it potentially reduces the thermal load on the electronics.  But is that really an advantage if the thermal load is merely being shifted to the transducer instead?  Also, as I understand it, one big problem with switching devices is EMI.  Supposedly, the EMI problem is reduced or eliminated in this design by using the transducer itself as the filter.  But does this really solve the EMI problem?  In an amp, unwanted EMI emissions are contained via a sealed metal chassis.  If the transducer itself is acting as the filter, wouldn't it be necessary to have EMI shielding around the transducer itself?  How is that supposed to work when the transducer must produce sound and is partly composed of soft, non-metal parts?

Again, this is not my area of expertise, so my criticism may not be correct.  However, this kind of things smacks of someone who is an amp expert thinking they know enough about transducers to realize this concept.  Reality may be much different.  It reminds me of those who obsess over amp distortion ratings, insisting that amp A is better than amp B becuase it has 0.01% THD instead of 0.1% THD.  Many of these people are EEs who definitely know what they are doing when it comes to electronics, but it apparently never occurred to them that 0.1% THD is about the best that anyone every realizes in a transducer and even then, only at low input levels.

Another point is that innovation has addressed many of the limitations of class D designs of that era.  The "made in USA" Speakerpower subwoofer amps are well over 90% efficient, albeit not suitable for high frequency reproduction.  IIRC ICE's amps, which are suitable for high frequencies, possess efficiency in the 80s%.  It would seem that most of the benefits of their concept can be realized by simply designing different kinds of amps for high frequency and low frequency duty without compromising much flexibility or over-complicating the design process.

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3 hours ago, radulescu_paul_mircea said:

Soon to come , report about cardioid directivity trough interference from Merlijn Van Veen. I will check it frequently to see what news we will get 

https://m.facebook.com/story.php?story_fbid=2537646626376057&id=1871382083002518

He has some good articles on his site if some of you are unfamiliar with it.

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