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Post by Keith M on May 5, 2014 15:24:16 GMT -5
Basically if you can feel it, you can record it. Sound moves as pressure waves through the air, and it excites receptors in our ears that is sent to our brain through nerves, or something like that. The range of what our ears hear is limited though, but we know that the sound exists outside our range, think of dog whistles and bat sonar and stuff like that.
A 20Hz wave is 20 cycles per second, below that frequency, our ears don't process it. But if that "sound" is loud enough you'll feel it. Microphones have parts that move/vibrate when sound pressure hits them and that is converted into an electrical signal, so they essentially feel sound much like our bodies can. Some may not detect all frequencies, and some may have filters added to remove certain frequencies, but some will pick it all up. Some microphones are very much like speakers, just working in reverse. In fact if you plug your headphones into a microphone jack you can use them as poor microphone. So if a sound can be created by mechanical means it can probably be recorded by similar methods.
As for why it's recorded, again it comes down to harmonics. It's the way different sound frequencies interact with one another, which affects how we perceive it. Of course when it's LFE, it's mostly about moving stuff, and thus making the presentation more engaging.
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Post by jmilton on May 5, 2014 15:33:49 GMT -5
...then I have a CD of "Dog Whistles Greatest Hits" I will sell you. As a bonus, I'll throw in a CD of 16-14hz ping pong effects, where you can toggle between them back-n-forth.  I guess as a pipe organ nut, I have never really appreciated the deepest notes. A 64 foot stop can go as low as 16hz... in real life. But I don't know if that has ever been recorded onto an actual commercial disc. Anybody have one they want to share?
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Post by frenchyfranky on May 5, 2014 17:52:55 GMT -5
My actual SVS PB2-plus can go down to 16 Hz at -3dB in the SPL range of 115-120 dB. For sure when movie LFE go that low I couldn't hear it, but I can confirm you that I feel the low-freq wave vibration on my stomach and my a$$...  I really don't need a buttkicker under my chair.  |
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Post by Deleted on May 5, 2014 22:02:58 GMT -5
Why it's recorded is because some people have systems that can reproduce it. My systems flat to 5HZ, although you may not be able to hear past 18hz, you sure as hell can experience it! I had an editor of popular mechanics come to my place 2 weekends ago when he was in the city for business, messaged me on AVS and came over for a listen. We played some Hulk, WOTW, black hawk down, battlefield L.A. and his face was priceless. +9 dB's over reference for BHD and my screen came right off it's mounts and fell to the ground lol. No damage but he left with one heck of a grin!
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Post by frenchyfranky on May 5, 2014 22:53:52 GMT -5
Why it's recorded is because some people have systems that can reproduce it. My systems flat to 5HZ, although you may not be able to hear past 18hz, you sure as hell can experience it! I had an editor of popular mechanics come to my place 2 weekends ago when he was in the city for business, messaged me on AVS and came over for a listen. We played some Hulk, WOTW, black hawk down, battlefield L.A. and his face was priceless. +9 dB's over reference for BHD and my screen came right off it's mounts and fell to the ground lol. No damage but he left with one heck of a grin! I must admit that your subs section is very impressive, maybe excessive for the majority of people. |
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Post by Deleted on May 6, 2014 0:49:45 GMT -5
Low sounds may be inaudible to the ear but felt or 'experienced in other ways. There are plenty of recorded test tones available with tones down to 5 or 10Hz (one such is at: www.audiocheck.net/audiotests_frequencychecklow.php) so yes, they have of course been' recorded'....but as many have said, but not so much in everyday music (some synth music, in movies and pipe organ etc). While not about music what is interesting are these effects themselves...many arguments abound about the human organism being able to detect these, but it's not always about the ears it seems. Take wind turbines and the problem that many swear is ruining their lives: ...Wind turbine produce infrasound which may be inaudible or audible.
A spectral analysis of sounds emitted at a Michigan site revealed that unweighted peak levels at frequencies under 5 Hz exceeded 90 dB SPL (Wade Bray, pers. comm., 2009). [36]
“There is no doubt that some humans exposed to infrasound experience abnormal ear, CNS, and resonance induced symptoms that are real and stressful.” [37]
There is no scientific consensus that infrasonic noise below the threshold of hearing will have no effect on health. There is scientific uncertainty regarding the understanding of human response to infrasound.
“There is no consensus whether sensitivity below 20 Hz is by a similar or different mechanism than sensitivity and hearing above 20 Hz…” [38]
In a 2009 Environmental Review Report [39] for an Ontario, Canada wind turbine project the consultant acknowledged that regarding wind turbine low frequency noise (LFN) and adverse health effects:
“It is acknowledged that LFN may be one area of scientific uncertainty in the wind industry as a whole.”
and regarding wind turbine infrasound:
“…it is recognized that this may be an area of scientific uncertainty.”
The National Research Council states “Low-frequency vibration and its effects on humans are not well understood. Sensitivity to such vibration resulting from wind-turbine noise is highly variable among humans…. studies on human sensitivity to very low frequencies are recommended.” [40] So maybe your everyday sub isn't going to produce 5Hz at 90 db in all situations, but then installing a wind turbine with balanced digital outs in your lounge room is really going to trigger the testy subject of the WAF scenario... Note: same may be said overall for high frequencies - we cannot (mostly) 'consciously' hear above 20Khz but then the effects of sound above this are little understood. Some feel that including frequencies above 20Khz adds 'dimension' and 'realism' etc to recordings, that we somehow 'feel' it makes music more enjoyable. I'm open to it but not decided yet - I do know we're more than just our ears ( and eyes, nose etc) when it comes to experiencing life. |
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