October 19, 2004

More on Kerry's French

As reported earlier, I downloaded the Kerry clip from Slate, reduced the noise level, and listened to it. Having listened to it again after some food, I now concur with the news report that what he said was: "Vous êtes de Haîti? D'accord. Je vais aider les Haîtiens." The problem with the clip is not Kerry's French; it's the dreadful quality of the recording.

To begin with, there is a lot of noise, including the cheering and shouting of the crowd and probably various other sources. Secondly, the recording is badly clipped. That means that the signal level was too high for the analog-to-digital converter, which chopped off the signal when it was above or below the maximum and minimum. This causes distortion. You can see the clipping in the sound pressure waveform below. When the waveform is square against the top and bottom it has been clipped. The highlighted section at the end is the part where Kerry speaks French.

Sound pressure waveform of Kerry clip

A final factor is that the clip was in MP3 format, compressed to 64k bits per second. MP3 compression is lossy, meaning that it removes information from the signal. The amount of distortion this produces depends on the bitrate. So-called "near CD quality" MP3s use a bitrate of 128k bits/second, twice that of the clip. I don't know if the compression had much of an effect - the original recording was evidently pretty bad to begin with - but lossy compression doesn't help.

If you want to listen yourself, here is my noise-reduced version of the relevant section, as linear PCM data in wav file format KerryFrench.wav [635,744 bytes] and compressed using the lossless FLAC method KerryFrench.flac [293,768 bytes]. Of course, using FLAC compression on a file already distorted by MP3 compression doesn't undo the distortion.

Posted by Bill Poser at October 19, 2004 10:04 PM