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NNTP-Posting-Date: Fri, 20 Jan 2006 14:36:31 EST
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Date: Fri, 20 Jan 2006 19:36:31 GMT
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On 2006-01-20 (ScottDorsey) said:
Try notch filters. Sweep around and find the fundamental, then
notch it out. Try the second and third harmonics, then keep going
up the scale until you're happy with the intelligbility. Odds are
the fundamental will be at 60 Hz, of course, but with some things
like electric motors it might be a touch lower. Use the narrowest
notch you can.
true enough. HOwever a couple of questions spring to mind:

DId you monitor what you were getting at all? IF so then
that begs the second question which is:

wHy did you record the "hum" in the first place?

HEy that's right, we can download software to fix anything
hrrrumph. Lack of technique capturing what you want never
enters the picture, cause anybody can do this.
NO knowledge or skill required, just put up a microhpone,
plug it into something, press record and dink with software
later.

hrrrumph

Hi,
I have a recording of a meeting that I attended but it's difficult to
make out some of what was said due to a relatively loud constant hum on
the recording. How can I eleiminate the hum to make the speech audible?

I could supply a clip of the soundtrack as a wav file if that would
help. I'm also looking for a freeware or shareware program that would
enable me to filter out the hum.

Any ideas anyone?

Flyn.

"flyn" wrote ...
I have a recording of a meeting that I attended but it's difficult to
make out some of what was said due to a relatively loud constant hum
on
the recording. How can I eleiminate the hum to make the speech
audible?

I could supply a clip of the soundtrack as a wav file if that would
help. I'm also looking for a freeware or shareware program that would
enable me to filter out the hum.

Any ideas anyone?

You can use a freware software like Audacity or a
cheapware software like GoldWave, or any number
of high-end software to do this. Some applications
(like Adobe Audition which I use) have preset filter
settings for doing this.

Note that you may have more than just the "fundamental"
frequency (50Hz or 60hz depending on where you live).
You may very well also have several "harmonics"
(multiples) of the line/mains frequency (50-100-150-200Hz
or 60-120-180- 240Hz, etc.)

Of course, it is always more desirable to eliminate hum
(and particularly other types of noise) while recording
rather than trying to remove them after the fact.

flyn wrote:
I have a recording of a meeting that I attended but it's difficult to
make out some of what was said due to a relatively loud constant hum on
the recording. How can I eleiminate the hum to make the speech audible?

I could supply a clip of the soundtrack as a wav file if that would
help. I'm also looking for a freeware or shareware program that would
enable me to filter out the hum.

Try notch filters. Sweep around and find the fundamental, then notch it
out. Try the second and third harmonics, then keep going up the scale
until you're happy with the intelligbility. Odds are the fundamental
will be at 60 Hz, of course, but with some things like electric motors
it might be a touch lower. Use the narrowest notch you can.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" wrote in message
...
flyn wrote:
I have a recording of a meeting that I attended but it's difficult to
make out some of what was said due to a relatively loud constant hum on
the recording. How can I eleiminate the hum to make the speech audible?

I could supply a clip of the soundtrack as a wav file if that would
help. I'm also looking for a freeware or shareware program that would
enable me to filter out the hum.

Try notch filters. Sweep around and find the fundamental, then notch it
out. Try the second and third harmonics, then keep going up the scale
until you're happy with the intelligbility. Odds are the fundamental
will be at 60 Hz, of course, but with some things like electric motors
it might be a touch lower. Use the narrowest notch you can.
--scott

it might be air handleing noise as well
some progams will let you sample the noise then they will take anything
with that sample sigiture out of the digital file
IMO the results are not worth the effort though
George

"flyn" wrote in message
ups.com...


I have a recording of a meeting that I attended but it's difficult to
make out some of what was said due to a relatively loud constant hum on
the recording. How can I eleiminate the hum to make the speech audible?

If the problem is really bad, this may be mission impossible.

However, vast improvements are possible if you have software that flexibly
implements a bank of narrow band filters. Adobe Audition is one such
program, and a free evaluation version can be downloaded from the Adobe
site.

In Audition there are a number of ways to implement narrow-band filters. My
current favorite is the "DTMF" filter feature. You can set the filter
frequencies by typing in numbers, and you have a choice of a few different
bandwidths.

You just filter with narrow-band filters at the power line frequency and its
harmonics. Sometimes you need to go through the 10th or 15th harmonics to
get the best possible results.

IOW in the US we filter at 60, 120, 180, 240, 360, 420, 480 etc. Hz.

George Gleason wrote:
"Scott Dorsey" wrote in message
...
flyn wrote:
I have a recording of a meeting that I attended but it's difficult to
make out some of what was said due to a relatively loud constant hum on
the recording. How can I eleiminate the hum to make the speech audible?

I could supply a clip of the soundtrack as a wav file if that would
help. I'm also looking for a freeware or shareware program that would
enable me to filter out the hum.

Try notch filters. Sweep around and find the fundamental, then notch it
out. Try the second and third harmonics, then keep going up the scale
until you're happy with the intelligbility. Odds are the fundamental
will be at 60 Hz, of course, but with some things like electric motors
it might be a touch lower. Use the narrowest notch you can.

it might be air handleing noise as well
some progams will let you sample the noise then they will take anything
with that sample sigiture out of the digital file
IMO the results are not worth the effort though

Air handling noise is usually a mixture of a motor hum and modulated
white noise. The sampled gadgets work very well on the motor hum (or
on any repetitive noise) but they can't do anything about the modulated
random noise.

For the most part, the sample-nulling systems are more transparent than
notch filters, but if your goal is just intelligibility they don't buy
you anything much.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" wrote in message
...

George Gleason wrote:

"Scott Dorsey" wrote in message
...

flyn wrote:
I have a recording of a meeting that I attended but it's difficult to
make out some of what was said due to a relatively loud constant hum on
the recording. How can I eleiminate the hum to make the speech audible?

I could supply a clip of the soundtrack as a wav file if that would
help. I'm also looking for a freeware or shareware program that would
enable me to filter out the hum.

Try notch filters. Sweep around and find the fundamental, then notch it
out. Try the second and third harmonics, then keep going up the scale
until you're happy with the intelligbility. Odds are the fundamental
will be at 60 Hz, of course, but with some things like electric motors
it might be a touch lower. Use the narrowest notch you can.

IME, good advice.

it might be air handleing noise as well
some progams will let you sample the noise then they will take anything
with that sample sigiture out of the digital file
IMO the results are not worth the effort though

One gets better results with software like this, the more you work with it.
Superficial approaches can be frustrating.

A person can get a lot of experience with dealing with HVAC and
lighting-induced noise while making recordings of live events.

Air handling noise is usually a mixture of a motor hum and modulated
white noise.

Agreed.

Casual recordings often do contain a lot of true and genuine hum - some from
fluorescent lights, some from HVAC sources as you say Scott, and some due to
bad signal wiring, equipment, or cable routing etc.

The sampled gadgets work very well on the motor hum (or
on any repetitive noise) but they can't do anything about the modulated
random noise.

Apparently some programs have learned some new tricks. One is to set up a
noise gate based on the amplitude of the noise sample that was provided.
This can be surprisingly effective.

Another is to identify frequencies where the sampled noise peaks (if it
peaks and that's not guaranteed of course), and drop in some specific
filtering for them.

sample-nulling systems are more transparent than
notch filters, but if your goal is just intelligibility they don't buy
you anything much.

I think of cleaning up recordings as a strategy game. It seems like every
time I play, I get a little better at it. Every once in a while some of the
people who do a lot of it, spill a few of their tricks and techniques.

wrote in message
...

On 2006-01-20 (ScottDorsey) said:
Try notch filters. Sweep around and find the fundamental, then
notch it out. Try the second and third harmonics, then keep going
up the scale until you're happy with the intelligbility. Odds are
the fundamental will be at 60 Hz, of course, but with some things
like electric motors it might be a touch lower. Use the narrowest
notch you can.
true enough. HOwever a couple of questions spring to mind:

DId you monitor what you were getting at all? IF so then
that begs the second question which is:

wHy did you record the "hum" in the first place?

HEy that's right, we can download software to fix anything
hrrrumph. Lack of technique capturing what you want never
enters the picture, cause anybody can do this.
NO knowledge or skill required, just put up a microhpone,
plug it into something, press record and dink with software
later.

hrrrumph

I find "software solutions" much more agravating than just recording it
right to begin with
and for me recording it right usually involves some sort of back up and
headphone monitoring
George

On 20 Jan 2006 07:00:05 -0800, "flyn" wrote:

I have a recording of a meeting that I attended but it's difficult to
make out some of what was said due to a relatively loud constant hum on
the recording. How can I eleiminate the hum to make the speech audible?

I could supply a clip of the soundtrack as a wav file if that would
help. I'm also looking for a freeware or shareware program that would
enable me to filter out the hum.

Yup. Put a sample wav file (don't compress to MP3) on a web page.
Then we can talk about the problem more productively.