I have a wedding that was taped years ago (15+) and have saved it to dvd. I extracted the audio and need some help getting the hiss/hum out. I’ve been trying different methods, but each result still leaves some background noise or digitizes the voices too much. Can I send someone a small clip so you know what I’m talking about? thank you, j
Oh I had that problem a while ago, apparently there’s many ways to reduce noise and humming. But there’s been quite a good way to do it.
Anyhow, some software has automatic noise suppression, I don’t know about audacity but I know soundforge can, plus theres like tons of settings in sound forge. So play around with it and see which ones the best. It isn’t free but I just used the trail version to do it. There’s no limitations other than 30 days. Usually what happens is if the noise is lower volume than the voice or whatever sound that you want. Than usually you cut down on the lower volume by clipping it, search on the internet for tutorials as to how to do that…
There are other ways, and I somewhat tried them out. Sometimes your sound gets a bit weird… But yea…
I just tried Sound Forge - It get’s rid of the hiss a little bit, but then the hum is still there and it won’t clear that. Can I send you a short sample?
Sorry, don’t have it anymore. There’s no real absolute way to do it. You can reduce it a little bit but if you cut down all the hiss the the quality of the sound that you want goes all funny. You just have to keep tweaking the settings. And try and get it the best you can.
Instructions for using the Audacity noise reduction tool are here: http://www.audacityteam.org/wiki/index.php?title=Noise_Removal
If the noise is at quite a high level you will not be able to remove it completely without making the remaining audio sound strange (bubbly or metallic echo type artifacts).
Note that the noise removal tool in v.1.3.4 uses a different algorithm from the noise removal tool in 1.2.6 - depending on the recording you will probably find that one version works better than the other, so it is worth trying both versions.
Stevethefiddle - thanks for the advise. I’m trying 1.3 now. I started with that but didn’t have good results. I think it’s mainly due to the quality to begin with. Can I send you a 8sec sample? Thanks John
Check your PM’s (“new messages” listed at top of page).
This is quite a challenge for any audio program - the signal level is very low and the noise very high - it’s not going to be possible to make it sound perfect.
The first thing I did, since it is a mono recording, was to convert it to mono(split track > delete one track > Set the remaining track to “mono”) and normalise to 0dB (“Edit->Amplify”).
So here is the mono track that I worked on: http://easyspacepro.com/audacity/testsample.wav (1.6 MB)
The settings that I quote below are not optimal settings, they are my “first attempt” settings.
Noise reduction in Audacity 1.3.4 is quite different from v.1.2.6, so I tried both. Overall I think 1.3.4 performed slightly better, but it’s always a trade off between quality, noise and artifacts.
The plug-ins that I used are available in the plug-in packs linked from the main Audacity website.
Audacity 1.2.6
The “noise” element is broadband (high and low frequencies), but the audio (speech) is mostly mid range, so the first thing was to eliminate much of the noise by simple filtering:
- Low pass filter at 2.5 kHz 24 dB per octave
- High pass filter 400 Hz - 24 dB per octave
- DC offset removal (this will generally improve the performance of noise removal processes, but in this case was probably not necessary)
Listening to the noise, you can hear a low pitched hum and a crackly hiss. Noise removal will be more effective if we can deal with these separately.
- Duplicate track
- Low pass filter track 1 at 1.2 kHz - 24 dB per octave
- High pass filter track 1 at 1.2 kHz - 24 dB per octave
- Select a section of noise from track 1, open the “Noise Removal” effect and click on “Get Noise Profile”.
- Select all of track 1, open the “Noise Removal” effect and set the “step 2” amount to about 15% (near to the last “s” of “Less”)
- Click on “Remove Noise”.
- Repeat steps 7-9 for track 2
Listening to each of these tracks individually (select “solo”) I could hear audio artifacts (bubbly metallic type sound) on both tracks - the artifacts were mostly mid frequencies, hence step 11)
11) By running steps 5) and 6) again, the artifacts could be reduced .
-
Run “Project → Quick Mix” to combine the tracks back together
-
Amplify to 0dB
-
Using a “Gate” effect (LADSPA plug-in) it was possible to reduce the noise between the talking.
The settings I used on the “Gate” were:
LF = min
HF = max
Threshold = -20dB
Attack = 50 ms
Hold = 90 ms
Decay = 50 ms
Range = -90
Output = 0
The final result is here: http://easyspacepro.com/audacity/clean%201.2.6.wav (1.6 MB)
Audacity 1.3.4
Basically the same technique, just a few small changes.
I set the project to 48000 Hz and worked in 32 bit float, converting back to 44.1/16 at the end.
In the initial “Low pass filter” (step 2) I ran it at 3 kHz for a bit more clarity to the voice.
The Noise reduction settings in steps 7) to 10) were approximately as follows:
Noise Reduction = 40 dB
Frequency Smoothing = 300 Hz
Attack/Decay time = 0.2
I didn’t bother with the second filtering stage (step 11) as there were far less “artifacts”
The result before gating is here: http://easyspacepro.com/audacity/clean%201.3.4.wav (1.6 MB)
and after gating: http://easyspacepro.com/audacity/clean%201.3.4%20gated.wav (1.6 MB)
As I said, the exact settings above are not “optimal” but they should give you an idea. After a bit of tweaking, I got this using Audacity 1.3.4 http://easyspacepro.com/audacity/clean%201.3.4%20alt2%20gated.wav (1.6 MB)
Just to give an idea of how difficult it is for a program to deal with audio this bad, this is the result using professional quality (expensive) software - you will notice that it is still far from perfect: http://easyspacepro.com/audacity/clean%20pro.wav (1.6 MB)
You are the man! Holy cow - I’ve been playing with 1.2.6 and following your steps listed. I’ve saved a sample but the main question I have now is on your steps (below)1.2.6 only has cut off freq - not the options like 1.3.4.
- Low pass filter at 2.5 kHz 24 dB per octave
- High pass filter 400 Hz - 24 dB per octave
I would like to get all the steps down right before jumping back into 1.3.4.
thanks again
Quite correct jhoski (deliberate mistake? 
)
I was in a bit of a hurry, scribbling down notes as I went, then copied them out in the post. The “24 dB/octave” refers to v.1.3.4, in v.1.2.6 it is just the cut-off frequency that you set.
Here you go John:
Using Audacity 1.2.6 (Exported as mp3 for smaller files and quicker downloads)
Original sample: http://easyspacepro.com/audacity/testsample.mp3
or as a wav: http://easyspacepro.com/audacity/testsample.wav
-
Low pass filter 6000 Hz
http://easyspacepro.com/audacity/1.mp3 -
High pass filter 300 Hz
http://easyspacepro.com/audacity/2.mp3 -
Low pass at 600 Hz
http://easyspacepro.com/audacity/5.mp3 -
Duplicate with High pass at 600 Hz
http://easyspacepro.com/audacity/6.mp3 -
Low frequency track (from step 5) with noise removal set to min (noise sample selected from this track)
http://easyspacepro.com/audacity/7-low.mp3 -
High frequency track (from step 6) with noise removal set to min (noise sample selected from this track)
http://easyspacepro.com/audacity/10-hi.mp3
11A) Low frequency track (from step 7) with Low Pass filter at 400, then High Pass filter at 300, then amplified by 6 dB.
http://easyspacepro.com/audacity/11a.mp3
11B) High frequency track (from step 10) with High Pass filter at 1500, then Low Pass filter at 2000 Hz, then amplified by 6 dB.
http://easyspacepro.com/audacity/11b.mp3
-
11A and 11B mixed and amplified to 0 dB (+5 dB amplification)
http://easyspacepro.com/audacity/13.mp3 -
Gate settings:
LF key: 800
HF key: 2000
Threshold: -53dB
Attack: 30ms
Hold: 600ms
Decay: 300ms
Range: -30dB
Output: 0 (gate)
http://easyspacepro.com/audacity/14.mp3