Notch Filter Preference and Tinnitus

[charlieF]

I'm experimenting with music in order to lessen the tinnitus in my right ear. It involves filtering out one(1) octave of music around the frequency of the tone in my ear that only I can hear. There was a recent study in Germany that had good results with this. I've tried to use Audacity's notch filter but have had a hard time removing just one octave. Other products let you plug in the frequencies to be removed - this is one thing that I would like to see changed or explained as to how I can take out the octave using the current configuration. When I've used other software the notch turns out looking like a straight highway, I don't get this with Audacity.

All of the music that I now listen to has to be notched filtered. I would love to find a way, using a plug-in or app or whatever, that could simultaneously filter out the frequencies so that I could listen to any format without doing so much work.

Millions of people suffer from Tinnitus all over the world.

[kozikowski]

Strictly, that's not a notch filter. That's a band reject filter. Notch filters manage one frequency.

You may make good use of the Equalization Effect.

http://kozco.com/tech/audacity/voiceEq.jpg

The blue line is a rubber band and you can push frequencies up and down as you wish. In Audacity 1.3, you can tailor the attenuation and save a curve for later once you find one that works.

I read a piece that you can get the ringing to vanish by generating an identical pitch tone.

Koz

[charlieF]

Hi Koz,

So what I'm using is a band reject filter? In other words, this is what I am doing when I remove from 3200Hz to 6300 to take out an octave surrounding the 4215Hz frequency, which is the tone of the ringing in my ear. I'm trying to get the Equalization working in the same way but the music doesn't sound or look like what I'm doing. Maybe I'm setting the 'Length of Filter" at the wrong setting. If I can get the equalizer to take out what I want, I could essentially do this with any player with a graphic equalizer and just play the music without so much work. An app like this would attract a lot of interest for there are so many sufferers out there, mostly older who could never be able to notch their music like this.

An Identical pitch tone, I believe, only serves to "mask" the sound so that it gets cancelled out, some hearing aids have this effect. There is really no cure at the moment, that is why there are so many quack remedies for this. What I'm trying to do lessens the sound ,but doesn't remove it. I hope it works-I enjoy music anyway, that is how I got Tinnitus.

Thanks,


Charlie

[steve]

Audacity does not have a built in band reject filter, but here's a plug-in that will do it.

bandstop.ny.zip

version 1.0 now superseded by version 1.1

(1.02 KiB) Downloaded 2502 times

[Updated version (1.1) here: http://forum.audacityteam.org/viewtopic ... 42&t=54196 ]

To "install" the plug-in, just extract the "bandstop.ny" file from this zip file and copy it into the Audacity plug-ins folder (the plug-ins folder is in the Audacity program folder which on Windows is usually in C:Program Files )
The plug-in requires a recent version of Audacity 1.3.x

I think it's pretty obvious how to use it, but if you have problems just ask.

[charlieF]

Hi Steve,

Thanks for the plug-in, it's exactly what I was looking for and reproduces the notch exactly as I want it.

Is there such an mp3 player or etc that can do this without reprocessing the music for all us music lovers that turned up the volume to high?

Thanks,

Charlie

[kozikowski]

<<<reproduces the notch exactly as I want it.>>>

It's still not a notch filter. A notch filter has one peak at the bottom at one frequency. A band reject filter has a defined attenuation at a range of frequencies which is your goal. It's possible the other software package found it convenient to extend the notch programming to more than one frequency and just didn't see any value in renaming it. If you encounter a notch filter in the hardware world, it won't have more than one effective frequency unless it's broken.

I assume Steve wrote it for you. You're holding original artwork. Enjoy it.

I don't know of any music player that will do what you want unless there is a graphic equalizer built into the program. iTunes has such an equalizer, but it doesn't have nearly the range or granularity you require.

Koz

Picture 5.png (126.91 KiB) Viewed 19728 times

[charlieF]

Koz,

I took a look at the other program, which is Wavepad by NCH. Under Effects-Equalizer they have Notch and Band Stop. The only difference between the two is that Band Stop has Start, End, Slope Length(Hz) and Amplitude(%), Notch has similar settings, but lacks the Slope Length. Slope length means nothing to me at this point. I'm happy with the way Audacity functions now with the Band Stop feature.

Would a Parametric Equalizer plug-in be able to play music that I want via a mp3 player etc?

Here's an interesting article about Pete Townsend and Tinnitus

http://www.rttnews.com/ArticleView.aspx ... 006&SMap=1

Thanks,

Charlie

[steve]

Back in the days when we made filters from resistors, capacitors, some wire and a soldering iron, a "Notch Filter" was typically based on a "Twin T" circuit. The idea of this circuit is that it was "perfectly" tuned to filter out one frequency. Of course in reality it was never "perfectly" tuned to one frequency, but it would give a very high degree of attenuation at the tuned (centre) frequency and the degree of attenuation would diminish rapidly for frequencies further away from the centre frequency. The response of the filter was a distinctive V shape (as seen in picture below). The "Q" (filter Quality) is a measure of how selective the filter is. Below is the spectrum of White Noise that has been filtered with a notch filter with a centre frequency set at 1000 Hz and a Q factor of 1.0. A higher Q factor will give a more narrow notch.

1kHz notch Q=1.0

notch.png (54.21 KiB) Viewed 19714 times

To produce a "band pass" or a "band stop" filter, a low-pass filter would be combined with a high-pass filter to create the required characteristics. The plug-in posted previously has a very high Q factor (the Q factor is increased as the band width is decreased to provide a high degree of rejection for narrow bands). With a band-stop (band reject) filter, the characteristic "shape" is quite different from the notch filter, as can be seen in this spectrum.

band-stop, centre frequency = 1000Hz, band width = 1 octave

band-stop.png (55.58 KiB) Viewed 19710 times

Parametric filters are useful in that you can set the centre frequency, the "Q" and the amount of gain (boost or cut at the centre frequency). A parametric filter that is set with very high Q and the gain set very low will produce a response similar to a notch filter, though the "notch" will not be as deep. A "Graphic" filter is similar to a series of parametric filters that each have fixed Q and have centre frequencies that are (evenly) spaced across the audible frequency range. The Q of graphic bands is typically quite high (broad frequency spread), though on a 30 band Graphic Equalizer the band width of each filter will be around 1/3 octave.

If you want to have a go with a notch filter, here is one that I've adapted from the notch filter written by David R Sky.

notch.ny.zip

(512 Bytes) Downloaded 746 times

The original version of this notch filter is available here: http://audacityteam.org/download/nyquistplugins

[charlieF]

Steve,

The BandStop was exactly what I was looking for. About 2 months ago, I was using the Notch Filter, but wasn't getting the results I wanted.

One more question. If I used a 30 Band Equalizer and removed an octave what would it look like?

Thanks,

Charlie

PS How do I upload pictures like you are doing so I can show you what my waves look like?

[kozikowski]

You get it from the numbers on the bottom of the graph. An octave is half or double. An octave up from A-440 (oboe at the beginning of the orchestra) is A-880.

There are a number of hearing anomalies when you start to dig in this stuff. People hear a "middle" tone at A-440 but on a linear frequency scale, it's no such thing. It's only in the "middle" if you consider an octave scale -- half and doubling -- like that illustration. Designing physical filters for real-time filtering is very different depending on which end of the piano you're trying to filter.

Also, in the "Q" or quality world, you only get really sharp, clean, well-behaved filters in digital. They tend to be sloppy and do the wrong things in the world of physical parts. Physical parts have one thing going for them, though. They operate in real time. Almost all digital services have to take time out and think about what they're doing and that makes delays. People doing multi-layer live recording on their PC run into the various delays and echoes almost immediately and you may, too, depending on the solution you settle on.

Koz