Thanks to Linda and Frank for a very interesting workshop last Friday. I picked up some great tricks on using transcriber and audacity. Perhaps the best trick I learnt was how to remove cicada noise from my PNG recordings.
Maybe you already knew how to do this (or maybe you just fiddle with the EQ), but I always thought this was in the realm of Hollywood fantasy (like when the forensics guy magically “enhances” a grainy image to reveal the killer’s face in a thriller). Removing the noise allows me to more easily transcribe a busy recording, and seeing as insect noise was pretty constant and loud through all my recordings, this is quite handy. There are some caveats, but here’s how to do this using freely available, cross platform software.
Step 1
Load your wav file in audacity and go to a quiet region. Select a portion of the background noise that you want to eliminate. Be sure that the selection is only made up of noise that you want to remove. Don’t select a section that has any voices in it, this won’t work. Likewise, animal noises within the speech range can’t be removed.
Step 2
Go to the “Effect” menu and select “Noise Removal…” and then click on “Get Noise Profile”.
Step 3
Select the entire sound (or the bit you want to remove noise from) and go again to “Noise Removal…”
Step 4
Make sure the slider bar is down near the “none” end of the scale. Too much noise removal will hinder your efforts by introducing artefacts (a.k.a. strange blippy noises). Click “OK”.
Step 5
Preview your changes, and try again if there’s too many artefacts. Select a cleaner quiet region, or lower the settings in the Noise Removal plug-in.
Step 6
Once your happy with it, export the file (always leave your original alone! This is just a temporary file to help you transcribe). Go to the “File” menu and select “Export As WAV”.
BONUS HANDY HINT!!!: Don’t use MP3 files with transcriber, there’s a bug in the program that messes up the time codes.
While you’re in Audacity, other useful things you can do include normalising the file and you can filter out the non-speech frequencies (below ~50Hz and above 8000Hz) using an EQ. This will (usually) boost the levels so you can hear better, and filter out any distracting noise.
While you may think all this is over the top, and I guess for a good recording it is, filtering out distracting noises can make it surprisingly easier to transcribe, and especially to pick up on the subtleties you missed the first time!
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Thanks for posting this! It’s very useful to have this information. I figured out how to remove noise using audacity awhile ago and have been using it for non-linguistics stuff. I’ve since been wondering if it was okay to do this with my field recordings. I’m glad to hear that others are doing it, and I think I might go give it a try! Plus, I’ve never tried these other useful things that can be done in audacity. The noise removal thing is the only part of it I’ve played with. I’ll definately have to try this to see if I can hear a bit more with some of my poorer quality recordings. I wonder, if you do this stuff, what kind of phonetic analysis can be done on the resulting sound file.
And thanks for that hint about using mp3s with transcriber. I have a friend who was just recently having problems with this, but we couldn’t figure out why.
By the way, I really think that this is a great blog you’ve set up, and it will be quite informative to a lot of us! Thanks!
Thanks Sheena. Regarding phonetic analysis, I’m not too sure. Presumably you’d be safer simply leaving it as is. There was a recent post on the linguist list on the viability of using poor quality audio for phonetic analysis here. They’re talking specifically about using files with (psycho-acoustic) compression… but I’m guessing it equally applies to this. Filtering out noise will always result in a loss of information. It definitely makes it easier to transcribe though!
I came across your article when googling for ways to suppress the noise of cicadas in my garden. Do you know of any electronic/other ways that we could do this please?
Many thanks.
Steve
short of agent orange? I can’t think of anything electronic, but encouraging birds in your garden will help, since they’ll eat the cicadas if they’re birds of the cicada-eating kind.
yes, not sure I can help you with your cicada problem sorry. Maybe invest in some ear plugs for a good nights sleep? Given they can be constant, I tend to get used them myself…