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Topic: Is There A Buzzing Sound In This Digitized Audio File? (Read 1477 times) previous topic - next topic
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Is There A Buzzing Sound In This Digitized Audio File?

I digitized a cassette tape the other day, and in an attempt to get a better copy I digitized that tape again today.

Audacity 2.4.2 was used to do the digitizing and the cleaning. The only cleaning done was Noise Reduction at default settings.

I do not know if it is just me hearing it, but can anyone else hear a slight harmonic or metallic ringing, or buzzing underneath the speakers words in the attached "After Cleaning" wav file?

If there is a buzzing underneath the speech. Is there anything that can be done about it?

Also attached the "Before Cleaning" wav file.

The digitized audio is for my own use. So it isn't like it necessarily needs to be perfect.

Re: Is There A Buzzing Sound In This Digitized Audio File?

Reply #1 –
The existing clicks have increased during your work. See the markers in the spectra. Audacity's declicker should solve the problem.

Re: Is There A Buzzing Sound In This Digitized Audio File?

Reply #2 –
Buzzing, low tonal frequencies have not been filtered out by audacity much, specially during speech periods they are easy to hear in denoised wav file. I get much better output when using spectral subtraction algorithm/filter.

Re: Is There A Buzzing Sound In This Digitized Audio File?

Reply #3 –
Quote from: rowi on
The existing clicks have increased during your work. See the markers in the spectra. Audacity's declicker should solve the problem.

This may sound like a stupid question.

Due to the cassette tape I had a need to record the volume at a lower than usual level. So I will eventually be using the sox utility to increase the volume level of the audio.

Should click removal be done on the original wav file before any noise reduction or volume normalization? or does it not matter in what order it is done?

Quote from: mycroft on
Buzzing, low tonal frequencies have not been filtered out by audacity much, specially during speech periods they are easy to hear in denoised wav file. I get much better output when using spectral subtraction algorithm/filter.

I am not familiar with the spectral subtraction algorithm/filter. I will read up on it.

Re: Is There A Buzzing Sound In This Digitized Audio File?

Reply #4 –
The problem with click removal is that it can negatively affect the actual audio. The attached sound files were made with Audacity 2.4.2 at default settings. With the current release, Audacity 3.7.3, the change to the audio is even more apparent.

I am not technically inclined enough to know what changes to make to the settings so that only real clicks are removed. I think I will be content with what I now have.

And really, the cause of the problem is with the audio on the cassette itself. The cassette is from a product made some twenty-five years ago, and leaves the feeling it was rushed out the door back then.

Re: Is There A Buzzing Sound In This Digitized Audio File?

Reply #5 –
SoX has some de-noising tools but you need to find places in the recording where the noise is on its own. Analyze 1 second of noise at 0:02:
Code: [Select]
sox "Before Cleaning.wav" -n  trim 2 1 noiseprof "profile.txt"
Reduce the noise:
Code: [Select]
sox "Before Cleaning.wav" "After Cleaning.sox.wav" noisered "profile.txt" 0.2

Re: Is There A Buzzing Sound In This Digitized Audio File?

Reply #6 –
Quote from: danadam on
SoX has some de-noising tools but you need to find places in the recording where the noise is on its own. Analyze 1 second of noise at 0:02:
Code: [Select]
sox "Before Cleaning.wav" -n  trim 2 1 noiseprof "profile.txt"
Reduce the noise:
Code: [Select]
sox "Before Cleaning.wav" "After Cleaning.sox.wav" noisered "profile.txt" 0.2

Does SoX have some sort of noise profile format (like text files) / syntax?
Could you attach a bunch of SoX noise profiles as a ZIP file?

Re: Is There A Buzzing Sound In This Digitized Audio File?

Reply #7 –
Quote from: MihaiPopa12346 on
Does SoX have some sort of noise profile format (like text files) / syntax?
Could you attach a bunch of SoX noise profiles as a ZIP file?
It's just power spectrum, 1025 numbers per channel.
https://sourceforge.net/p/sox/code/ci/f3094754a7c2a7e55c35621d20fa9945736e72df/tree/src/noiseprof.c#l94
Code: [Select]
Channel 0: 3.531723, 3.613256, ..., -1.348056, -1.527251
Channel 1: -4.016803, -3.973702, ..., -7.743027, -7.721468

Re: Is There A Buzzing Sound In This Digitized Audio File?

Reply #8 –
The problem with the audio that on the cassette is that the volume level is inconsistent from beginning to end.

For side_a and side_b of the cassette the majority of each sides audio stays at a consistent level. But the last part (guessing, the last thirty percent) of each side's audio the volume increases, and I do not know why it increased. It is as if the speakers on the cassette must have gotten closer to the microphone, or started speaking more loudly or something, especially the male speaker.

The first time the cassette was digitized I set the recording volume level based on the beginning volume of each sides audio, so that the meter in Audacity stayed out of the red. Which is fine, except when the audio gets to the last part of the side playing it is living in the red zone.

So on digitizing the audio again I set the recording volume level based on the volume level of the last section of each side's audio so that the Audacity meter stayed out of the red. Which of course means the beginning volume level of each side is real low.

As far as sox goes. I ran this command. And increased the volume by the specified 4.101 amount and the meter in Audacity was in the red for last sections of the digitized audio.

Code: [Select]
sox side_a.wav -n stat -v
4.101

I think I can live with what I now have.


Re: Is There A Buzzing Sound In This Digitized Audio File?

Reply #9 –
Quote from: cwb on
Which of course means the beginning volume level of each side is real low.
You could always get the first part of the first recording and the second part of the second recording and and join them together.

Re: Is There A Buzzing Sound In This Digitized Audio File?

Reply #10 –
Quote from: danadam on
Quote from: cwb on
Which of course means the beginning volume level of each side is real low.
You could always get the first part of the first recording and the second part of the second recording and and join them together.

That is an ingenious idea!

Now I would need to figure out exactly where in the audio the volume increase begins. Can you give any pointers on doing that?

Re: Is There A Buzzing Sound In This Digitized Audio File?

Reply #11 –
Quote from: cwb on
Quote from: danadam on
Quote from: cwb on
Which of course means the beginning volume level of each side is real low.
You could always get the first part of the first recording and the second part of the second recording and and join them together.

That is an ingenious idea!

Now I would need to figure out exactly where in the audio the volume increase begins. Can you give any pointers on doing that?


I think I got it. I'll just look at the waveform and see where the increase takes place.