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Re: 60 Hz hum causing problems with speech recognition

It figures, the Hz don't go as far in Europe as they do in the US.  Like the dollar...
-----Original Message-----
From: Piotr Majdak [mailto:piotr@xxxxxxxxxx]
Sent: Tuesday, June 16, 2009 11:38 AM
To: AUDITORY@xxxxxxxxxxxxxxx
Subject: Re: 60 Hz hum causing problems with speech recognition

In Europe, we call it "the 50-Hz hum" :-) Tarun, I also vote for a ground loop. You could look if you have more than one device grounded. If you have no grounded devices try to ground the mic-preamp. Usually this helps in our lab. Good luck, Piotr Pierre Divenyi wrote: > Tarun, you have two options: (1) get rid of the ground loop that is > quite probably the culprit, or (2) move to Europe where the 60-Hz hum > is unknown. > > -Pierre > > > On 6/16/09 7:43 AM, "Tarun Pruthi" wrote: > > Hi all: > > I have been having a lot of problems lately with 60 Hz humming > noise in my speech recordings (I will confess that most of my > tests have been on windows/linux laptops - and my guess is that > they probably have much worse recording quality than desktops on > average - but we live in a mobile world now and I have to make it > work on laptops). Whenever it is there, it causes a serious drop > in speech recognition accuracy, especially since it comes in very > randomly at times giving for example clean recordings during > speaker enrollment and noisy recordings in live testing. The > problem is even worse on linux which has given me all kinds of > artifacts in the recordings besides the 60 Hz hum - my guess is > that this is most likely because of driver problems. > > So, I have 3 questions: > 1. What is the source of this 60 Hz noise? Powerline? RF > interference? I have tried disconnecting the power cord - it works > sometimes, but not always. > 2. Is there a standard way to get rid of the 60 Hz hum and ensure > clean recordings for the purposes of speech recognition? The only > way I can think of is to use notch filters at 60 Hz, and some of > the harmonics, say 120 Hz and 180 Hz, since most of the times it > doesn't manifest as a single tone at 60 Hz, but has harmonics all > over the frequency range. > 3. If this is a well-known problem with sound cards, then why > aren't we, speech recognition community, trying to come up with a > mandatory compliance standard for sound card manufacterers which > ensures that the microphone input is not corrupted by 60/50 Hz > noise? That should provide a big boost to speech recognition > accuracies, and a wider acceptance of speech recognition. > > Tarun > Senior Research Engineer > Think A Move, Ltd > >