IDM Mailing Archive

This list is starting to look like a rec.audio digital/analog battle... %) So of course I can't resist throwing in $0.02: 1. The experiments that "showed" that people can detect (not consciously hear) sounds up to 100 kHz involved very high volume and transducers directly on the skull. In normal situations, very few people can hear much over 20 or maybe 23 kHz. If you could, things like ultrasonic motion detectors would drive people mad. Remember, the high pitched whine from a US TV set is only 15.75 kHz. Try playing a clean LP on a high-end setup and using an EQ to knock out everything below 16 kHz. What's left will typically have tons of phase distortion, noise, etc. 2. Ultrasonics don't influence lower, audible frequencies "by interference." This is a classic rec.audio claim, and you can verify that it doesn't happen by feeding sine waves of appropriate frequencies through a speaker with a good tweeter. You won't hear a beat frequency. A standard experiment is to make a 44.1 kHz digital recording of an LP and then compare the DAT of the LP to the original. Most reports are that no difference can be heard in blind tests. I would expect that, at least for idm type music, digital's ability to go right down to 0 Hz in the bass would be more relevant... The French police were able to cause all sorts of devastating (and personally embarassing) physical and emotional effects in rioters with very low frequency riot horns (5 Hz?). Obviously this has limited commercial application... "Fear Rave with DJ DC! Make sure to bring mouthwash and a change of clothes!"... %)

On Fri, 4 Feb 1994, Larry Spence wrote:

quoted 7 lines difference can be heard in blind tests. I would expect that, at least for

> difference can be heard in blind tests. I would expect that, at least for > idm type music, digital's ability to go right down to 0 Hz in the bass > would be more relevant... The French police were able to cause all sorts of > devastating (and personally embarassing) physical and emotional effects in > rioters with very low frequency riot horns (5 Hz?). Obviously this has > limited commercial application... "Fear Rave with DJ DC! Make sure to > bring mouthwash and a change of clothes!"... %)

Yeah, it may go down to 0 Hz, but no amplifier would amplify these signals. Virtually all amplifiers cut off below ~50 Hz. You can do more than just make people shit themselves, I personally don't fancy being eviscerated by the sub-bass I love :) Incidently this amplifer point is interesting in that quite a few amplifiers, cut out all frequncies above 25 kHz anyway. So the people who are claiming that vinyl is better because you get lot of really high end stuff >25 kHz, better check their Amplifier specs!!!!! greg 3 0 3

On Fri, 4 Feb 1994, Larry Spence wrote:

quoted 7 lines I would expect that, at least for

> I would expect that, at least for > idm type music, digital's ability to go right down to 0 Hz in the bass > would be more relevant... The French police were able to cause all sorts of > devastating (and personally embarassing) physical and emotional effects in > rioters with very low frequency riot horns (5 Hz?). Obviously this has > limited commercial application... "Fear Rave with DJ DC! Make sure to > bring mouthwash and a change of clothes!"... %)

Bring it on! :) (of course there'll be someone selling "Disco Diapers" at the vendor table) | Dave Walker, Detroit Art Services (DAS) | | "I don't read, I just guess" | | marmoset@msen.com -Happy Mondays, "Wrote For Luck" |

quoted 8 lines 1. The experiments that "showed" that people can detect (not consciously

> 1. The experiments that "showed" that people can detect (not consciously > hear) sounds up to 100 kHz involved very high volume and transducers > directly on the skull. In normal situations, very few people can hear > much over 20 or maybe 23 kHz. If you could, things like ultrasonic > motion detectors would drive people mad. Remember, the high pitched > whine from a US TV set is only 15.75 kHz. Try playing a clean LP on a > high-end setup and using an EQ to knock out everything below 16 kHz. > What's left will typically have tons of phase distortion, noise, etc.

quoted 5 lines 2. Ultrasonics don't influence lower, audible frequencies "by interference."

> 2. Ultrasonics don't influence lower, audible frequencies "by interference." > This is a classic rec.audio claim, and you can verify that it doesn't > happen by feeding sine waves of appropriate frequencies through a speaker > with a good tweeter. You won't hear a beat frequency. >

I'm open minded about this. I suspect that if an effect does exist, it's gonna be small, and not worth worrying about unless you're getting into the realms of ultra-hi-fi. I accept (1) and (2), though with the proviso that some people can apparently hear sounds well above 20kHz. The question is, can the presence of an inaudible unltrasonic signal imfluence your perception of the sounds in the audio range....? There's some experimental evidence that the brain detects the untrasonic signal, and we don't really understand the processes involved in the perception of sound, so it's certainly plausible.... As to whether it matters for the purposes of this discussion, probably not, but....

quoted 4 lines Yeah, it may go down to 0 Hz, but no amplifier would amplify these

> Yeah, it may go down to 0 Hz, but no amplifier would amplify these > signals. Virtually all amplifiers cut off below ~50 Hz. You can do more > than just make people shit themselves, I personally don't fancy being > eviscerated by the sub-bass I love :)

How about modulating (shifting) the ~0Hz signals up to some acceptable frequency range, amplifying, and then demodulating back down?

quoted 1 line 3 0 3

> 3 0 3

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