Tones below 100Hz result in a high pitched squeak

[noingwhat]

I was looking for a tone that sounded like an earthquake, and I heard around 7Hz is what an earthquake sounds like. So I put in a chirp 7-8 Hz, and all I hear is a high pitched noise. I cant figure out why. I thought maybe something was wrong with my speakers, so I tried hooking it up to my stereo system, and still the same thing. I was expecting to see my subwoofer move back and fourth slowly, but instead, it will just make that hight pitched noise up until somewhere around 100Hz. Why is it doing this, a few months ago when I was messing around, and I would get the speaker to move slowly without the chirp. What is going on and how do I fix it?

Thanks all.

[kozikowski]

One of the tricks with producing earthquake sounds is not to start and stop the tones too quickly. In real life (trust me on this) the 7Hz motion builds up relatively slowly and the house starts rocking back and forth. That's why if you ask three people when the quake started, you get three different answers.

If the real life quake is right under you, the shock wave starts the motion abruptly and can be heard as cracking or rumbling. So to simulate The Real Thing, you need to fade in the tone over a quarter-second or half-second or so. I think those are the "B" waves -- the rolling motion.

As to why your speakers didn't move back and forth, anything below 20Hz is considered "not sound" and may or may not be managed by the sound system. How did you have the "music" routed to the speaker? Trace the wires. Laptop out to the amplifier through an adapter cable and then to the speaker? Any equalizer or loudness boosters set on the amplifier? Turn all those off.

Koz

[Gale Andrews]

I just composed this while Koz was replying (you're in an earthquake zone - right Koz)? Anyway since the reply is largely different I'm going to post it as it was...

Can you hear 7 Hz? The generally accepted range of human hearing is 20 Hz - 20 kHz. Look at a second of your waveform - can you see 7 distinct peaks? If not you didn't generate a 7 Hz chirp.

One approach may be to generate white noise and apply Effect > Change Speed at -50% a couple of times to it.

If you want real earthquake sounds a simpler solution may be to obtain or record some samples from the internet.



Gale

[kozikowski]

<<<you're in an earthquake zone - right Koz>>>

That's like asking someone if they have any boating stories. Get a nice cuppa....

<<<generate a 7 Hz chirp. >>>

You can't generate a 7 Hz "chirp." It violates all the Fourier rules. You're generating a mathematical abstraction not traceable to real life.

<<<One approach may be to generate white noise and apply Effect > Change Speed at -50% a couple of times to it. >>>

That's a new one. The generally accepted theatrical version is to subject the white noise to a low pass filter. "Hollywood" insists on seeing a wine glass walk off the table spilling as it goes and that takes the "A" waves. Those are the ones described as "Truck Going By, Grumbling, Growling, or Rumbling. The usual accompaniment to that is the sound of glass breaking. So the upper end of those is actually audible even past the sound of your house falling apart.

We are warned not to confuse the sound of speaker cones turning themselves into scrap paper with being able to hear 7 Hz.

If you've been here long enough, you can tell where the quake is by which waves you experience.

The best email discussion I ever authored was over the existence of "Earthquake Weather."

Koz

[Gale Andrews]

<<<One approach may be to generate white noise and apply Effect > Change Speed at -50% a couple of times to it. >>>

That's a new one. The generally accepted theatrical version is to subject the white noise to a low pass filter.

Maybe the Change Speed is more like a tornado? Someone told me once that's how they generated earthquake sounds, so just passing it on...


Gale

[noingwhat]

Ok, well I have realized that it is for some reason not playing the sounds. My computer appears to be filtering out the lower pitched noises. I checked that all enhancements were disabed, and I tried changing the sample rate, yet still nothing. I tried slowing the white noise down, and it seems like that may have worked somewhat, But it is extremely quiet.

[kozikowski]

Good low frequency "sound" is expensive. I'm not shocked that your $8 USD sound card will not pass 7 Hz. I bet it has troubles passing anything below 100Hz.

That's why I was wondering how you got it to work the first time. What was your pipeline when you were watching your speaker cones go in and out?

I wonder if I can get that to work here......

Koz

[noingwhat]

Same setup before.... Only thing I can think of is I believe that last time I did that was with Vista, now I am running windows 7. Same computer, same stereo, same hookup. Nothing is different other than that.

[kozikowski]

Cool. Let's see if we can force the issue. Generate two or three seconds of the following:

120 Hz
60 Hz
30 Hz
15 Hz
7 Hz

First play music and make sure you didn't do anything silly. Does the music sound normal? Good and bassy?

Play the tones in sequence. You can hear 120, but the others should be all but inaudible to you. You should be able to gently touch the speaker cone and feel it vibrating. Good music systems will be at full volume (vibration) through 30 and then gently fade at 15 and a more aggressive fade at 7. The blue waveforms on the timeline should all be the same size.

Koz