Thankyou. very interesting. Env Health officers always state third octave and BS4241 when conducting indoor low frequency testing yet the BS states this standard not to be used for low frequency, use NANR45! Accredited noise consultants have all spoken to me about using the FFT, even the manufacturer of the councils instrument. (though the council only have the third octave software despite the instrument upgrading to fft) Is a "spectrum analyser" a general term which can also apply to third octave only instruments?
A constant-Q analyzer looks good in a music player with logarithmic scale and a 3db slope for higher frequencies, avoiding mosf of the signal being compressed on the left side with high frequecies only utilizing a fraction of the display height. All bands are maximally responsive. But no music player actually has this type of analyzer. There are some VST plugins for a DAW. In a music player these plugins are usually not delay compensated. A downside of this method is the slope of the filters is low, and a single tone excites a range of bands. There is also some minimum phase ringing with narrow filters, but it is fine because an analyzer usually has a slow falloff speed, and an FFT needs additional smoothing to achieve that at small sizes. FFT always has a low time resolution regardless of the processing power. With more overlap it'll just swell up more gradually. There is a trick where multiple FFTs can be taken and long windows used for low frequencies, and short ones for high. But this brute force approach is extremly slow.
Exactly what I was looking for - thank you!
Thankyou. very interesting. Env Health officers always state third octave and BS4241 when conducting indoor low frequency testing yet the BS states this standard not to be used for low frequency, use NANR45! Accredited noise consultants have all spoken to me about using the FFT, even the manufacturer of the councils instrument. (though the council only have the third octave software despite the instrument upgrading to fft) Is a "spectrum analyser" a general term which can also apply to third octave only instruments?
A constant-Q analyzer looks good in a music player with logarithmic scale and a 3db slope for higher frequencies, avoiding mosf of the signal being compressed on the left side with high frequecies only utilizing a fraction of the display height. All bands are maximally responsive. But no music player actually has this type of analyzer. There are some VST plugins for a DAW. In a music player these plugins are usually not delay compensated.
A downside of this method is the slope of the filters is low, and a single tone excites a range of bands. There is also some minimum phase ringing with narrow filters, but it is fine because an analyzer usually has a slow falloff speed, and an FFT needs additional smoothing to achieve that at small sizes.
FFT always has a low time resolution regardless of the processing power. With more overlap it'll just swell up more gradually.
There is a trick where multiple FFTs can be taken and long windows used for low frequencies, and short ones for high. But this brute force approach is extremly slow.
It is a really fantastic lecture.!!!!!