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Topic: Record low to mid human hearing range (Read 3896 times) previous topic - next topic
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Record low to mid human hearing range

I'm looking for a way to record and somehow display the results of frequencies in the bottom to mid range of the human ear. The human ear can hear between 20 and 2000 hz with some reports saying humans can hear as low as 12hz. I'm only interested in the low frequencies like the vibration of electricity passing through the over head power lines.

Can someone please offer some suggestions from a plain English, layman point of view.

Many thanks.
Christian

Record low to mid human hearing range

Reply #1 –
Quote from: ccsalway on
I'm looking for a way to record and somehow display the results of frequencies in the bottom to mid range of the human ear. The human ear can hear between 20 and 2000 hz with some reports saying humans can hear as low as 12hz. I'm only interested in the low frequencies like the vibration of electricity passing through the over head power lines.

There's nothing special to recording those frequencies. Many microphones are sensitive in this range.

There are a few practical issues you may have to deal with. For example, if you use directional microphones made for singers on stage, you will notice that they are less sensitive at low frequencies to compensate for the proximity effect. Don't use those. You will probably be served best by an omnidirectional microphone.

You may also have to deal with wind noise, particularly when recording outdoors. Even indoors, air motion (such as drafts caused by air conditioning) may get picked up as very low frequency rumble. There are accessories available for many microphones to counteract this. There are foam windshields, or fur-coated baskets, for example. You may be tempted to use an equalizer to remove those frequencies, but since you are interested in recording low frequencies, you may have problems finding a good compromise setting.

You can use a computer as a recorder, or there are a large number of different recorders available, with various degrees of portability. We would need to have more information about your application to recommend anything in particular. An idea of the available budget would also help.

Record low to mid human hearing range

Reply #2 –
Quote
I'm looking for a way to record and somehow display the results of frequencies in the bottom to mid range of the human ear.
Audacity (FREE) can record but you'd record the entire frequency range and then you can optionally kill-off the higher frequencies with a low-pass filter (easy with Audacity).

By default, Audacity will show you a normal (time domain) waveform.    If you have a pure tone you can zoom-in to figure-out the period & frequency, but with normal audio which contains many frequencies that's not helpful.   

To the left of the waveform display, there is a little drop-down arrow where you can select the Spectrogram View and that will help you analyze the frequency content.

You might want to play around with some existing WAV or MP3 files before you start recording.

You can also generate tones with Audacity.  (That might be helpful if you want to compare generated tones with whatever you record.)

Quote
The human ear can hear between 20 and 2000 hz with some reports saying humans can hear as low as 12hz.
The "traditional" hearing range is 20 - 20,000Hz for a young person with normal hearing.    The ear is most sensitive at around 2kHz.  Although 2kHz is in the lower part of the audible range linearly, it's in the upper part logarithmically and it's perceived as a 'high pitch". 

Very low frequencies are usually felt with the body (any maybe with the ears) rather than being "heard" as a "tone".

Microphones don't have perfectly flat frequency response.  They are generally less-sensitive at very-low and very-high (audio) frequencies.  Of course, good studio mics are better than cheap "computer" mics.  Power line frequency is either 50Hz (Europe) or 60Hz (North America).    Any microphone should pick that up with no problem.

It's the same with speakers...  It takes a very-good speaker to reproduce the whole audio range.  When you get down around 20Hz, it takes BIG woofers (or subwoofers) and BIG amplifiers to get usable output.

Quote
I'm only interested in the low frequencies like the vibration of electricity passing through the over head power lines.
50 or 60Hz is a low-frequency "hum".    What I've heard  from power lines not a pure 60hz hum, but rather is usually a "buzz", which is either 60 Hz harmonics or noise (such as from an arc) modulated at 60Hz.  In Audacity, you can generate a pure 50 or 60Hz sine wave (hum), or you can generate a square wave which contains lots of harmonics.

Record low to mid human hearing range

Reply #3 –
To be picky, and to the best of my knowledge, electricity itself never makes any sound unless there is arcing, such as lightning. Electrons can't move normal (dry) air molecules. Sometimes electricity in a wire vibrates other nearby physical objects and excites them to make noise though and we may describe it as "the electricity in the wire is causing a sound". Also a cable in the wind, even a wind we don't notice as "wind" can be excited to the point of vibration or the magnetic field of the wire in proximity to other (metal) objects, for instance at the ends of the wire miles away, can set it into motion over its entire length, but none of these are technically "electricity passing through a wire makes noise, such as hum".

Some electrical components, such as transformers, make noise too (due to magnetostriction) and this can be carried down the wire, for miles, much like the problem we have in audio called microphone (or headphone) cord chaffing noise, which is often improperly referred to as "microphonics" by some.

Record low to mid human hearing range

Reply #4 –
Quote from: ccsalway on
Can someone please offer some suggestions from a plain English, layman point of view.


Use a microphone and a computer/tablet/smartphone. 

Record low to mid human hearing range

Reply #5 –
These are all excellent replies. Thank you so much.

Basically there is a hum in my house that is driving me crazy and im trying to find the source. I've turned the power off to the whole house but there's still a very low hum. There are power lines that run under the foundation which I'm wondering if they are causing it or whether the neighbours garage has something running, but until I can source where, I don't want to go knocking on doors. Ironically the hum isn't on the top floor of my house, hence my suspicions.

I have a mac book air with built in mic so will try that first although I'm not so good with audicity

Record low to mid human hearing range

Reply #6 –
If it's a really low frequency, it may come from much farther. It will also probably interfere with itself in various locations in your house, making it hard to pinpoint by volume (as is my experience trying to pinpoint weird hums of medium- and high frequencies).

Record low to mid human hearing range

Reply #7 –
Quote from: ccsalway on
I have a mac book air with built in mic so will try that first although I'm not so good with audicity

Just be sure that you are operating on battery or else you could get AC pickup from the power cord.

Also, turn off/unplug any appliances and lights.

Record low to mid human hearing range

Reply #8 –
Are you hearing this hum through your audio system?
Or is it the air even with your equipment unplugged?
Kevin Graf :: aka Speedskater
 

Record low to mid human hearing range

Reply #9 –
Quote from: ccsalway on
... There are power lines that run under the foundation which I'm wondering if they are causing it ...


If the sound is coming from/through the structure of your house, hold, eg, a screwdriver against walls, floor, etc, and hold the handle against your ear. Or wasn't there an old eavesdropping trick of holding a glass beaker against the wall, and holding your ear to that? I think I remember that from children's stories!
The most important audio cables are the ones in the brain