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#1
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multi-band equalizer
For CD signals (sampling rate 44100Hz), Butterworth method is applied to
design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? |
#2
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multi-band equalizer
"WYChen" wrote in message ... For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? What difference would it make one way or the other? Set sampling that low, and you will have what sounds like a cheap AM radio with a ten band graphic equalizer. -Dave |
#3
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multi-band equalizer
"WYChen" wrote in message ... For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? What difference would it make one way or the other? Set sampling that low, and you will have what sounds like a cheap AM radio with a ten band graphic equalizer. -Dave |
#4
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multi-band equalizer
"WYChen" wrote in message ... For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? What difference would it make one way or the other? Set sampling that low, and you will have what sounds like a cheap AM radio with a ten band graphic equalizer. -Dave |
#5
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multi-band equalizer
"WYChen" wrote in message ... For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? If you sample at 1/4 the sampling rate then all those frequencies you listed will be lowered by a factor of 1/4. That is, the frequencies of your new filter would be 15.75 Hz, 31.25 Hz, 62.5 Hz, 125 Hz, ..., 4 kHz. That means your corresponding weights will be messed up as you'll be emphasizing frequencies at 1/4 the frequency you were before. So if you removed any filters you should remove the "low" filters since at the new sampling rate your "high" filter will be at 4 kHz. Also as someone else pointed out sampling at 11.025 kHz will make the sound pretty crappy. The highest frequency you could have in your signal would be 5.5125 kHz. For comparison a telephone gives you 3 kHz for your maximum frequency so you're not doing too much better! Brad |
#6
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multi-band equalizer
"WYChen" wrote in message ... For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? If you sample at 1/4 the sampling rate then all those frequencies you listed will be lowered by a factor of 1/4. That is, the frequencies of your new filter would be 15.75 Hz, 31.25 Hz, 62.5 Hz, 125 Hz, ..., 4 kHz. That means your corresponding weights will be messed up as you'll be emphasizing frequencies at 1/4 the frequency you were before. So if you removed any filters you should remove the "low" filters since at the new sampling rate your "high" filter will be at 4 kHz. Also as someone else pointed out sampling at 11.025 kHz will make the sound pretty crappy. The highest frequency you could have in your signal would be 5.5125 kHz. For comparison a telephone gives you 3 kHz for your maximum frequency so you're not doing too much better! Brad |
#7
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multi-band equalizer
"WYChen" wrote in message ... For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? If you sample at 1/4 the sampling rate then all those frequencies you listed will be lowered by a factor of 1/4. That is, the frequencies of your new filter would be 15.75 Hz, 31.25 Hz, 62.5 Hz, 125 Hz, ..., 4 kHz. That means your corresponding weights will be messed up as you'll be emphasizing frequencies at 1/4 the frequency you were before. So if you removed any filters you should remove the "low" filters since at the new sampling rate your "high" filter will be at 4 kHz. Also as someone else pointed out sampling at 11.025 kHz will make the sound pretty crappy. The highest frequency you could have in your signal would be 5.5125 kHz. For comparison a telephone gives you 3 kHz for your maximum frequency so you're not doing too much better! Brad |
#8
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multi-band equalizer
In alt.music.mp3.hardware Brad Griffis wrote:
"WYChen" wrote in message ... For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? If you sample at 1/4 the sampling rate then all those frequencies you listed will be lowered by a factor of 1/4. That is, the frequencies of your new Err, no. That'd be the case if you wanted a 9 band graphic equaliser, designed for 0-5512Hz, but you don't. Leave the frequencies as they are, and just ignore the last two, will give as similar effect as you can get. You get the same output signal, minus any frequencies past around 5Khz. |
#9
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multi-band equalizer
In alt.music.mp3.hardware Brad Griffis wrote:
"WYChen" wrote in message ... For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? If you sample at 1/4 the sampling rate then all those frequencies you listed will be lowered by a factor of 1/4. That is, the frequencies of your new Err, no. That'd be the case if you wanted a 9 band graphic equaliser, designed for 0-5512Hz, but you don't. Leave the frequencies as they are, and just ignore the last two, will give as similar effect as you can get. You get the same output signal, minus any frequencies past around 5Khz. |
#10
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multi-band equalizer
In alt.music.mp3.hardware Brad Griffis wrote:
"WYChen" wrote in message ... For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? If you sample at 1/4 the sampling rate then all those frequencies you listed will be lowered by a factor of 1/4. That is, the frequencies of your new Err, no. That'd be the case if you wanted a 9 band graphic equaliser, designed for 0-5512Hz, but you don't. Leave the frequencies as they are, and just ignore the last two, will give as similar effect as you can get. You get the same output signal, minus any frequencies past around 5Khz. |
#11
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multi-band equalizer
WYChen wrote:
For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? Changing sample rate to 11.025 kHz requires, that your analog input signal is band-limited to frequencies lower than Fs/2=5.5 kHz. If this is not the case, you'll get aliasing errors. If you use the same filter (i.e. the same coefficients) with 1/4 of the original sample rate, you'll get a filter with 1/4 of the original band frequency, which is 8, 16, 31, 62.5, 125, 250, 500, 1K, 2K, 4KHz Since you don't need the lowest two filters, you could remove them together with the weights from the higher end. Should result in 8 bands as: 31, 62.5, 125, 250, 500, 1K, 2K, 4KHz 0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6 My guess is, that the weights will not work as fine as before, because the lack of high frequency content misleads the ear. You'll probably do better with bigger values for the higher frequencies. But that's guessing - I didn't try it... Bernhard |
#12
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multi-band equalizer
WYChen wrote:
For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? Changing sample rate to 11.025 kHz requires, that your analog input signal is band-limited to frequencies lower than Fs/2=5.5 kHz. If this is not the case, you'll get aliasing errors. If you use the same filter (i.e. the same coefficients) with 1/4 of the original sample rate, you'll get a filter with 1/4 of the original band frequency, which is 8, 16, 31, 62.5, 125, 250, 500, 1K, 2K, 4KHz Since you don't need the lowest two filters, you could remove them together with the weights from the higher end. Should result in 8 bands as: 31, 62.5, 125, 250, 500, 1K, 2K, 4KHz 0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6 My guess is, that the weights will not work as fine as before, because the lack of high frequency content misleads the ear. You'll probably do better with bigger values for the higher frequencies. But that's guessing - I didn't try it... Bernhard |
#13
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multi-band equalizer
WYChen wrote:
For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? Changing sample rate to 11.025 kHz requires, that your analog input signal is band-limited to frequencies lower than Fs/2=5.5 kHz. If this is not the case, you'll get aliasing errors. If you use the same filter (i.e. the same coefficients) with 1/4 of the original sample rate, you'll get a filter with 1/4 of the original band frequency, which is 8, 16, 31, 62.5, 125, 250, 500, 1K, 2K, 4KHz Since you don't need the lowest two filters, you could remove them together with the weights from the higher end. Should result in 8 bands as: 31, 62.5, 125, 250, 500, 1K, 2K, 4KHz 0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6 My guess is, that the weights will not work as fine as before, because the lack of high frequency content misleads the ear. You'll probably do better with bigger values for the higher frequencies. But that's guessing - I didn't try it... Bernhard |
#14
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multi-band equalizer
Thanks for all responses.
We will try it. WYChen "Bernhard Holzmayer" ??? ???... WYChen wrote: For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? Changing sample rate to 11.025 kHz requires, that your analog input signal is band-limited to frequencies lower than Fs/2=5.5 kHz. If this is not the case, you'll get aliasing errors. If you use the same filter (i.e. the same coefficients) with 1/4 of the original sample rate, you'll get a filter with 1/4 of the original band frequency, which is 8, 16, 31, 62.5, 125, 250, 500, 1K, 2K, 4KHz Since you don't need the lowest two filters, you could remove them together with the weights from the higher end. Should result in 8 bands as: 31, 62.5, 125, 250, 500, 1K, 2K, 4KHz 0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6 My guess is, that the weights will not work as fine as before, because the lack of high frequency content misleads the ear. You'll probably do better with bigger values for the higher frequencies. But that's guessing - I didn't try it... Bernhard |
#15
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multi-band equalizer
Thanks for all responses.
We will try it. WYChen "Bernhard Holzmayer" ??? ???... WYChen wrote: For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? Changing sample rate to 11.025 kHz requires, that your analog input signal is band-limited to frequencies lower than Fs/2=5.5 kHz. If this is not the case, you'll get aliasing errors. If you use the same filter (i.e. the same coefficients) with 1/4 of the original sample rate, you'll get a filter with 1/4 of the original band frequency, which is 8, 16, 31, 62.5, 125, 250, 500, 1K, 2K, 4KHz Since you don't need the lowest two filters, you could remove them together with the weights from the higher end. Should result in 8 bands as: 31, 62.5, 125, 250, 500, 1K, 2K, 4KHz 0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6 My guess is, that the weights will not work as fine as before, because the lack of high frequency content misleads the ear. You'll probably do better with bigger values for the higher frequencies. But that's guessing - I didn't try it... Bernhard |
#16
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multi-band equalizer
Thanks for all responses.
We will try it. WYChen "Bernhard Holzmayer" ??? ???... WYChen wrote: For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? Changing sample rate to 11.025 kHz requires, that your analog input signal is band-limited to frequencies lower than Fs/2=5.5 kHz. If this is not the case, you'll get aliasing errors. If you use the same filter (i.e. the same coefficients) with 1/4 of the original sample rate, you'll get a filter with 1/4 of the original band frequency, which is 8, 16, 31, 62.5, 125, 250, 500, 1K, 2K, 4KHz Since you don't need the lowest two filters, you could remove them together with the weights from the higher end. Should result in 8 bands as: 31, 62.5, 125, 250, 500, 1K, 2K, 4KHz 0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6 My guess is, that the weights will not work as fine as before, because the lack of high frequency content misleads the ear. You'll probably do better with bigger values for the higher frequencies. But that's guessing - I didn't try it... Bernhard |
#17
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multi-band equalizer
"Ian Stirling" wrote in message ... In alt.music.mp3.hardware Brad Griffis wrote: "WYChen" wrote in message ... For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? If you sample at 1/4 the sampling rate then all those frequencies you listed will be lowered by a factor of 1/4. That is, the frequencies of your new Err, no. That'd be the case if you wanted a 9 band graphic equaliser, designed for 0-5512Hz, but you don't. Leave the frequencies as they are, and just ignore the last two, will give as similar effect as you can get. You get the same output signal, minus any frequencies past around 5Khz. Whoops - I left off the very first frequency band. The new filters would be at 7.75 Hz, 15.75 Hz, 31.25 Hz, 62.5 Hz, 125 Hz, ..., 4 kHz Ian, you're being misleading. In discrete-time filtering the cutoff frequencies are always between 0 and pi radians. This corresponds to 0 and Fs/2 in the original analog signal. If you change your sampling rate that doesn't matter to your discrete signal. Its cutoffs are still somewhere between 0 and pi. The thing that changes is the corresponding "analog" frequency. This is why changing your sampling rate by a factor of 4 changes all the positions of the filters by the corresponding factor of 4. Brad |
#18
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multi-band equalizer
"Ian Stirling" wrote in message ... In alt.music.mp3.hardware Brad Griffis wrote: "WYChen" wrote in message ... For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? If you sample at 1/4 the sampling rate then all those frequencies you listed will be lowered by a factor of 1/4. That is, the frequencies of your new Err, no. That'd be the case if you wanted a 9 band graphic equaliser, designed for 0-5512Hz, but you don't. Leave the frequencies as they are, and just ignore the last two, will give as similar effect as you can get. You get the same output signal, minus any frequencies past around 5Khz. Whoops - I left off the very first frequency band. The new filters would be at 7.75 Hz, 15.75 Hz, 31.25 Hz, 62.5 Hz, 125 Hz, ..., 4 kHz Ian, you're being misleading. In discrete-time filtering the cutoff frequencies are always between 0 and pi radians. This corresponds to 0 and Fs/2 in the original analog signal. If you change your sampling rate that doesn't matter to your discrete signal. Its cutoffs are still somewhere between 0 and pi. The thing that changes is the corresponding "analog" frequency. This is why changing your sampling rate by a factor of 4 changes all the positions of the filters by the corresponding factor of 4. Brad |
#19
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multi-band equalizer
"Ian Stirling" wrote in message ... In alt.music.mp3.hardware Brad Griffis wrote: "WYChen" wrote in message ... For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? If you sample at 1/4 the sampling rate then all those frequencies you listed will be lowered by a factor of 1/4. That is, the frequencies of your new Err, no. That'd be the case if you wanted a 9 band graphic equaliser, designed for 0-5512Hz, but you don't. Leave the frequencies as they are, and just ignore the last two, will give as similar effect as you can get. You get the same output signal, minus any frequencies past around 5Khz. Whoops - I left off the very first frequency band. The new filters would be at 7.75 Hz, 15.75 Hz, 31.25 Hz, 62.5 Hz, 125 Hz, ..., 4 kHz Ian, you're being misleading. In discrete-time filtering the cutoff frequencies are always between 0 and pi radians. This corresponds to 0 and Fs/2 in the original analog signal. If you change your sampling rate that doesn't matter to your discrete signal. Its cutoffs are still somewhere between 0 and pi. The thing that changes is the corresponding "analog" frequency. This is why changing your sampling rate by a factor of 4 changes all the positions of the filters by the corresponding factor of 4. Brad |
#20
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multi-band equalizer
In alt.music.mp3.hardware Brad Griffis wrote:
"Ian Stirling" wrote in message ... In alt.music.mp3.hardware Brad Griffis wrote: "WYChen" wrote in message ... For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? If you sample at 1/4 the sampling rate then all those frequencies you listed will be lowered by a factor of 1/4. That is, the frequencies of your new Err, no. That'd be the case if you wanted a 9 band graphic equaliser, designed for 0-5512Hz, but you don't. Leave the frequencies as they are, and just ignore the last two, will give as similar effect as you can get. You get the same output signal, minus any frequencies past around 5Khz. Whoops - I left off the very first frequency band. The new filters would be at 7.75 Hz, 15.75 Hz, 31.25 Hz, 62.5 Hz, 125 Hz, ..., 4 kHz Ian, you're being misleading. In discrete-time filtering the cutoff frequencies are always between 0 and pi radians. This corresponds to 0 and Fs/2 in the original analog signal. If you change your sampling rate that doesn't matter to your discrete signal. Its cutoffs are still somewhere between 0 and pi. The thing that changes is the corresponding "analog" frequency. This is why changing your sampling rate by a factor of 4 changes all the positions of the filters by the corresponding factor of 4. Well, yes of course if you leave the filter unchanged. But it's not going to obtain similar audio effects. To do that, you need to leave the frequency bands alone, and modify the filter so that this happens. |
#21
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multi-band equalizer
In alt.music.mp3.hardware Brad Griffis wrote:
"Ian Stirling" wrote in message ... In alt.music.mp3.hardware Brad Griffis wrote: "WYChen" wrote in message ... For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? If you sample at 1/4 the sampling rate then all those frequencies you listed will be lowered by a factor of 1/4. That is, the frequencies of your new Err, no. That'd be the case if you wanted a 9 band graphic equaliser, designed for 0-5512Hz, but you don't. Leave the frequencies as they are, and just ignore the last two, will give as similar effect as you can get. You get the same output signal, minus any frequencies past around 5Khz. Whoops - I left off the very first frequency band. The new filters would be at 7.75 Hz, 15.75 Hz, 31.25 Hz, 62.5 Hz, 125 Hz, ..., 4 kHz Ian, you're being misleading. In discrete-time filtering the cutoff frequencies are always between 0 and pi radians. This corresponds to 0 and Fs/2 in the original analog signal. If you change your sampling rate that doesn't matter to your discrete signal. Its cutoffs are still somewhere between 0 and pi. The thing that changes is the corresponding "analog" frequency. This is why changing your sampling rate by a factor of 4 changes all the positions of the filters by the corresponding factor of 4. Well, yes of course if you leave the filter unchanged. But it's not going to obtain similar audio effects. To do that, you need to leave the frequency bands alone, and modify the filter so that this happens. |
#22
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multi-band equalizer
In alt.music.mp3.hardware Brad Griffis wrote:
"Ian Stirling" wrote in message ... In alt.music.mp3.hardware Brad Griffis wrote: "WYChen" wrote in message ... For CD signals (sampling rate 44100Hz), Butterworth method is applied to design 10 bandpass filters. Center frequencies of these 10 bands a 31, 63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz, respectively. As weighting values (0.5, 0.5, 0.5, 0.8, 1.1, 1.3, 1.6, 1.6, 1.6, 1.6) are set to these corresponding 10 badns, the "Full Treble" style of music is achieved. It seems that the function of "Full Treble" is to emphasize the feeling of high frequency components . Question: If the sampling rate of input signal is changed to 11025Hz, should I modify the multi-band equalizer and the weighting values? Or just remove the last band (16KHz)? If you sample at 1/4 the sampling rate then all those frequencies you listed will be lowered by a factor of 1/4. That is, the frequencies of your new Err, no. That'd be the case if you wanted a 9 band graphic equaliser, designed for 0-5512Hz, but you don't. Leave the frequencies as they are, and just ignore the last two, will give as similar effect as you can get. You get the same output signal, minus any frequencies past around 5Khz. Whoops - I left off the very first frequency band. The new filters would be at 7.75 Hz, 15.75 Hz, 31.25 Hz, 62.5 Hz, 125 Hz, ..., 4 kHz Ian, you're being misleading. In discrete-time filtering the cutoff frequencies are always between 0 and pi radians. This corresponds to 0 and Fs/2 in the original analog signal. If you change your sampling rate that doesn't matter to your discrete signal. Its cutoffs are still somewhere between 0 and pi. The thing that changes is the corresponding "analog" frequency. This is why changing your sampling rate by a factor of 4 changes all the positions of the filters by the corresponding factor of 4. Well, yes of course if you leave the filter unchanged. But it's not going to obtain similar audio effects. To do that, you need to leave the frequency bands alone, and modify the filter so that this happens. |
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