Pre-emphasis and fricatives

[Evelyn W]

From my understanding, we apply pre-emphasis using something like a high-pass filter, boosting high frequencies to flatten the spectrum. I have couple of questions about this

1. Does it impact the representation/test accuracy of sounds with more energy at high-frequencies, like fricatives?

2. Can pre-emphasis amplify unwanted noise?

[Simon King]

Pre-emphasis is primarily to avoid numerical problems in taking the DFT of a signal with very different amounts of energy at different frequencies. Using too much pre-emphasis might have negative consequences by over-boosting high frequencies, but typically only modest pre-emphasis is applied.

Pre-emphasis will boost any non-speech at higher frequencies, yes. So, if that is noise then pre-emphasis will make the Signal-to-Noise Ratio (SNR) worse. Again, this should not be a problem with the modest amount of pre-emphasis typically used.

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