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Paper Tape
sbfuller
Posts: 5
Registered: ‎12-05-2011
Location: USA
0

Pseudo comb filter audio response with T420i

Since I got the machine I have updated it with all of the MS and Lenovo updates. I am running Windows 7 Professional 64 bit.  The audio sound quality is lacking high frequency content.  I finally did a series of tests where I played back a file of pink noise at a medium recorded level and connected the phone jack output to an external FFT analyzer. 

 

The output spectrum starts dropping at about 500 Hz and goes to a null at 1000 Hz and then repeats the null at 2 KHz and then the next null is at 4 KHz and then at 8 KHz just like a comb filter except this has octave nulls.

 

I get the same result with smart audio installed and with it uninstalled.

 

Any help would be greatly appreciated.

 

Thanks.

Retired Employee
Serge1410
Posts: 2,438
Registered: ‎04-10-2011
Location: Malaysia
0

Re: Pseudo comb filter audio response with T420i

hey sbfuller,

welcome to the forums.

could you explain more on what you're trying to do here?





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Paper Tape
sbfuller
Posts: 5
Registered: ‎12-05-2011
Location: USA
0

Re: Pseudo comb filter audio response with T420i

Hi Serge,

 

I found the audio quality of the sound to be unacceptable due to lack of higher frequencies.  In testing I found out why the sound quality is deficient.  It really does lack high frequency content starting at 1 kHz and repeating at octave intervals.  There is a significant lack of overtones in string music.  The frequency response looks like a comb filter except instead of having output nulls at linear frequency intervals the outpput nulls are at octave intervals.

 

I have never seen this in any PC or sound interface and it appears to be a defect, either in the conexant device or the drivers. 

Guru
ColonelONeill
Posts: 6,529
Registered: ‎12-26-2009
Location: Toronto
0

Re: Pseudo comb filter audio response with T420i

Did you try disabling audio enhancements under WIndows Sound?
W520: i7-2720QM, Q2000M at 1090/695/1390, 22GB RAM, 500GB HDD, FHD screen
TPT1: 1839-23U, stock ICS
X61T: L7500, 3GB RAM, 500GB HDD, XGA screen, Ultrabase
Paper Tape
sbfuller
Posts: 5
Registered: ‎12-05-2011
Location: USA
0

Re: Pseudo comb filter audio response with T420i

Hello ColonelONeill,

 

Thanks for the reply.  I disabled all audio enhancements.  When that did not fix the problem I removed the Conexant Smart Audio package.  That also failed to fix the problem.  I reinstalled the Smart Audio and again disabled all audio enhancements and that is where it stands now.

Guru
ColonelONeill
Posts: 6,529
Registered: ‎12-26-2009
Location: Toronto
0

Re: Pseudo comb filter audio response with T420i

Most interesting...

Post a picture? :smileytongue:
W520: i7-2720QM, Q2000M at 1090/695/1390, 22GB RAM, 500GB HDD, FHD screen
TPT1: 1839-23U, stock ICS
X61T: L7500, 3GB RAM, 500GB HDD, XGA screen, Ultrabase
Paper Tape
sbfuller
Posts: 5
Registered: ‎12-05-2011
Location: USA
0

Re: Pseudo comb filter audio response with T420i

I don't have an image on the web, just a bit map file.  I was unable to insert it as an image or paste the image from Word.  Is there any way I can email the bit map file?

 

Thanks.

                     

Paper Tape
sbfuller
Posts: 5
Registered: ‎12-05-2011
Location: USA
0

Re: Pseudo comb filter audio response with T420i

I was able to get a friend to post the image on:

https://plus.google.com/photos/115724595253329168035/albums/5694565325211002913?authkey=CIjA7fCA34W3...

 

I hope this helps.