Hearing extremely low and high frequency sounds through records?

Question

The human ear can only hear sounds in the 20Hz to 20kHz range. Is it possible, using an audio recorder, to record a sound beyond that range that we can't hear, but on playback be able to hear it? Basically, can an audio recorder change the frequency of what it records so we can hear it? Or is it a 'what you record is what you hear/is played back' type of deal? I personally think what is recorded is what you'd hear. But I've heard ideas that they may record what we can't hear but then on playback we can hear them. So just wondering.

Also, is there a device that CAN do this? Sound amplifiers (headphones you wear that amplify sound in a certain area) only amplify the Hz we can already hear, right? They don't let you hear sounds in Hz we can't hear?

Just wondering. Would be interesting, through those means if possible, to be able to hear things that we normally couldn't.

Answer 1

Only one way I think this could happen. Distortion introduces harmonics. If you record a frequency that is too low to be heard, < 20Hz, and you play it back using equipment that introduces distortion, you would be able to hear the harmonics of the low frequency even though you would not be able to hear the low frequency itself.

Answer 2

The problem with your question as you've asked it is that an audio recorder will do just that; record the range of human hearing. The audio circuits are not designed to process sounds at higher frequencies; although the basic limitations are (1) the microphone being used, and (2) the frequency recording characteristics of the record\playback of the device doing the recording.



There are devices in the scientific community that can record ultrasonic sounds and play them back so that the human ear can hear them. The process they use is to record the sound at a particular tape speed (say 15 inches per second) and play them back at a slower speed (for example, 7.5 or 3.75 inches per second. This would effectively halve or quarter the frequency, lowering the frequency of the recording to the range of human hearing. The faster the initial tape speed, and the slower the playback speed, determines the final playback frequency.



The trick here is to have both a microphone and recorder capable of capturing those ultrasonic vibrations. Think in terms of $$$ rather than $$.

Answer 3

Frequency shifting is one way, although I don't know if you can with a el cheapo recorder, you might be able to with a better recorder. Frequency shifting envolves changing the frequency that you can't hear to another one that you can hear. One why you can shift the frequency is to change the speed of the recording. Slowing down higher frequencies will reduce the frequency (if you can imaging listening to a recording on a cassette player when the batteries are dying).

Answer 4

Generally, mircophones record far less then the we can hear (usually ending somewhere around 15KHz.)

Using special (read: expensive) equipment, you can record ultra-low and high sounds. It can then be digitally edited to "move" the unhearable sounds to a better, more hearable frequency.



You'd probably need some professional audio-editing software to do it though, and I doubt there's an analog way to do it.

Answer 5

It can be done,by mixing the ultrasound or infra-sound with another frequency and using electronic filters will get a audible sound that is the exact replica of the initial sound(the same modulation another frequency)!!!!

Answer 6

Giraffes don't have vocal chords, so they don't grunt or say anything. A trampling of hooves and a munching of leaves may occasionally be heard from them.