Filter out frequencies below 10hz

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posword
Posts: 1
Joined: Sun Jan 29, 2006 12:47 am

Filter out frequencies below 10hz

Post by posword » Sun Jan 29, 2006 1:01 am

I'm doing a process of encoding speech mono .wav files to MP3, and have been asked to "filter out frequencies below 10hz" before encoding.

Can someone please tell me the steps to take using GoldWave, the effect to use, the settings, etc.

Many thanks

JackH
Posts: 100
Joined: Sat Mar 27, 2004 3:27 pm

Post by JackH » Sun Jan 29, 2006 4:55 am

Effect -> Filter -> Lowpass/Highpass is probably what you want. You'd set the initial cutoff to 20Hz (the lowest GW allows), choose "Highpass" and "Static" and then probably set the steepness to the maximum.

I'm not sure exactly how steep the steepest setting is; I don't see any specifics in the help or the manual, but that should attenuate frequencies of 10Hz and below substatially, though perhaps not entirely.

If it's not effective enough, you can run it multiple times, or look for a plug-in with a "brick wall filter," which attenuates very sharply.

donrandall
Posts: 549
Joined: Wed Dec 01, 2004 11:06 pm
Location: Denver, Colorado

Post by donrandall » Mon Jan 30, 2006 3:19 am

I'm doing a process of encoding speech mono .wav files to MP3, and have been asked to "filter out frequencies below 10hz" before encoding.
Below 10hz? Hmmmm......

I do voiceovers, and in my business, it is common to attenuate at 100hz and down - but 10?

Be aware that Goldwave does not cut it that fine, yet. Currently, you can get down to 20hz, but that's it. Since it is speech, it is unlikely that this would be a problem.

In any event, Goldwave does have a bandpass/bandstop filter which may help, you could also try the lowpass/highpass filter or the parametric equalizer.

Perticelli
Posts: 46
Joined: Wed Nov 09, 2005 2:41 pm

Post by Perticelli » Mon Jan 30, 2006 4:38 pm

i see the lowpass/high pass filter and the equalizer of the same and some other options under filter..can anyone tell us what they actually do and/or what you would use them for?

why filter out 10khz for voice over? what is attenuate mean and what does 100khz have to do with it?
im very curious..thx!

Skrewpa
Posts: 21
Joined: Thu Jul 21, 2005 2:10 am

Post by Skrewpa » Mon Jan 30, 2006 6:32 pm

Attenuate means to diminish. Listen to your stereo with the volume up. Now turn it down. You have attenuated the volume.

Lowpass filter lets you select a specific frequency and then attenuates all frequencies above the chosen frequency.

Highpass filter does the same thing only it attenuates frequencies below the selected frequency.

If you are familiar with a graphic equalizer, which has knobs or levers to boost or cut specific frequencies then it's not difficult to understand a parametric equalizer if you just picture the graphic eq with knobs or levers that can be re-assigned to different frequencies or added or removed as needed. You can also adjust how "wide" the levers are by setting the range of frequencies that a lever cuts or boosts.

If there is too much low rumble in a file, then try the highpass filter. Filtering speech below 100hz can give you more headroom so that you can boost the volume without low end distortion.

Use the parametric EQ to focus on very specific frequency ranges that you would like to cut or boost.

Perticelli
Posts: 46
Joined: Wed Nov 09, 2005 2:41 pm

Post by Perticelli » Wed Feb 01, 2006 9:57 am

wow, excellent explanation.
thx!

Skrewpa
Posts: 21
Joined: Thu Jul 21, 2005 2:10 am

Post by Skrewpa » Thu Feb 02, 2006 1:23 am

Perticelli wrote:wow, excellent explanation.
thx!
Yr Wlcme! :lol:

donrandall
Posts: 549
Joined: Wed Dec 01, 2004 11:06 pm
Location: Denver, Colorado

Post by donrandall » Thu Feb 02, 2006 7:56 pm

...what does 100khz have to do with it?
When equalizing for voiceover, it is common to cut from 100khz down because that is where extraneous ambient room noise - "room tone" - is generally to be found. A slight amount is acceptable, and probable even a good thing, but beyond that it is just undesirable noise that should be attenuated.

Another area that sometimes (often) needs attention is the frequency range in the 400 - 600 khz range (give or take a little, depending on the voice). This is the range where what is sometimes called "boominess" or "tubbiness" is found, and a slight bit of attenuation here can really clean up the sound.

The third area of concern is the higher frequencies, usually in the approximate range of 4000 - 8000 khz. To put some life in the voice track and bring it out and give it a little punch, a little boost here can help.

Experimeting with the settings and the amount of boost or cut is necessary because not all voices are the same and every microphone has it's own audio coloration.

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