RE: Ultrasonic

RE: Ultrasonic

Posted by tomservo (M) on March 12, 2012 at 11:00:06

In Reply to: Ultrasonic posted by Kloss on March 12, 2012 at 07:42:19:

Hi Kloss
I know also that one can synchronize and change ones state of consciousness using beat frequencies presented to each ear (entrainment I think they called it), in the 90’s they sold these “light and sound” machines for meditation and such. Also, we supplied a number of VLF transducers for preventing bowel adhesion's after surgery and for some kind of music therapy bed.

There is the nagging difficulty with ultrasonic energy within music though.
In the late 90’s I made a living as a for hire transducer designer and one job was for a professor at Northwestern U in Evanston il. He was researching the heterodyne loudspeaker which used ultrasonic energy and the air’s non-linearity to project sound. I built a focusing electrostatic speaker (the levitation transducers didn’t have enough bandwidth). At the point it was starting to hiss and crackle from high Voltage, that could produce about 160 dB at 55KHz at the focal point at 36 inches. To measure that high in frequency and SPL, required a TINY B&K microphone ($ huge $) who’s noise floor would be prohibitive for recording.
When you modulate the 55Khz carrier frequency and or amplitude, the non-linearity in the air produces an audible sound.
This same idea resurfaced several times since, one under his student Joe.
The problem is the fidelity is at best a tinny transistor radio and while the carrier was not audible per say, about half the test subjects complained about a headache after exposure suggesting the 55Khz was doing something.

The point is, when you have the stuff to measure up that high, you really find it is hard to reproduce sound that high up. When you consider aural masking, it is clear it could only be audible against a quiet background and with the equal loudness curves, only at a very high SPL.

Heck even if you can produce it and measure it, at 10MHz a strong airborne sound wave only travels a few inches before being fully absorbed, one guy selling magic super duper tweeters here was talking GHz frequencies (no kidding).

I agree with the frequency response observation and in fact most folks don’t realize that what one measures at the normal one meter, may be very different than what one would measure either indoors or out (no room effects) at the listening distance.
Just like with 99% of concert sound systems, the sound spectrum changes with distance and position if it isn’t constant directivity and even getting 20KHz to the listening position isn’t that easy..
Best,
Tom

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Follow Ups Full Thread

Topic - Ultrasonic Nonsense, speakers, etc. What do you guys think? - g_greenamyer@yahoo.com 20:48:58 03/11/12 (32)

I WANT the roaches and mice in the walls to enjoy themselves too... - Elizabeth 00:02:10 03/15/12 (1)

HA! Awesome post, Thank you - Sordidman 09:52:26 03/19/12 (0)

RE: Ultrasonic Nonsense, speakers, etc. What do you guys think? - Inmate51 08:25:42 03/13/12 (0)

RE: Did you know that... - BigguyinATL 06:56:19 03/13/12 (8)

RE: Did you know that... - Inmate51 08:42:21 03/13/12 (7)

RE: Did you know that... - tomservo 09:39:38 03/13/12 (6)

By non-linear do you mean that compression and rarifaction are not exact mirrors of one another? nt - viridian 13:27:52 03/13/12 (5)

RE: By non-linear do you mean that compression and rarifaction are not exact mirrors of one another? nt - Inmate51 14:18:14 03/13/12 (0)

RE: By non-linear do you mean that compression and rarifaction are not exact mirrors of one another? nt - tomservo 13:44:09 03/13/12 (3)

RE: By non-linear do you mean that compression and rarifaction are not exact mirrors of one another? nt - Inmate51 14:26:58 03/13/12 (2)

RE: By non-linear do you mean that compression and rarifaction are not exact mirrors of one another? nt - tomservo 14:59:12 03/13/12 (1)

RE: By non-linear do you mean that compression and rarifaction are not exact mirrors of one another? nt - Inmate51 07:59:44 03/14/12 (0)

RE: Ultrasonic Nonsense, speakers, etc. What do you guys think? - Ross 05:40:47 03/13/12 (0)

The Hypersonic World of Akira - 4season 16:09:33 03/12/12 (1)

RE: The Hypersonic World of Akira - Iron Knee 03:59:25 03/13/12 (0)

RE: Ultrasonic Nonsense, speakers, etc. What do you guys think? - Tony Lauck 15:38:32 03/12/12 (0)

I don't think that it is about more information, but about how that information is organized...... - viridian 08:48:28 03/12/12 (0)

RE: Ultrasonic Nonsense, speakers, etc. What do you guys think? - tomservo 05:55:51 03/12/12 (12)

In other words, you have no idea. - carcass93 14:57:45 03/12/12 (6)

RE: In other words, you have no idea. - tomservo 18:28:34 03/12/12 (5)

RE: In other words, you have no idea. - Inmate51 08:00:29 03/13/12 (4)

RE: In other words, you have no idea. - tomservo 08:16:53 03/13/12 (3)

RE: In other words, you have no idea. - Inmate51 14:44:52 03/13/12 (2)

RE: In other words, you have no idea. - tomservo 16:28:47 03/13/12 (1)

RE: In other words, you have no idea. - Tony Lauck 17:12:21 03/19/12 (0)

Ultrasonic - Kloss 07:42:19 03/12/12 (2)

RE: Ultrasonic - tomservo 11:00:06 03/12/12 (1)

RE: Ultrasonic - Kloss 13:05:16 03/12/12 (0)

"One can hear ultrasonic energy too if it's loud enough," - Kal Rubinson 07:11:45 03/12/12 (1)

You know I often - Presto 14:15:39 03/13/12 (0)

RE: Ultrasonic Nonsense, speakers, etc. What do you guys think? - RGA 05:49:42 03/12/12 (0)

wrong asylum - hifitommy 22:30:27 03/11/12 (0)

Follow Ups

RE: Ultrasonic - tomservo 11:00:06 03/12/12 (1)

RE: Ultrasonic - Kloss 13:05:16 03/12/12 (0)

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