Sounds "cracking" when interrupting speech

### Steps to reproduce

Running Orca, generate events quickly so speech for them gets interrupted often.

### Obtained behavior

Sometimes, I hear short "cracks" between speech requests.

### Expected behavior

No cracks, smooth audio.

### Behavior information

Not really sure, but I don't see overruns or underruns in system logs.

Happens with both espeak-ng and Baratinoo modules at least. Sound system is pulseaudio in both cases, but hardware is different, though both Intel HDA, s16le 2ch, 44100Hz.

### Distribution & Speech-Dispatcher version

Debian, someone with spd 0.9.0 (Buster) reproduces it, and I can also get it (Bookworm, 0.11.4), though much less frequent I believe.

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I would think the issue *might* be that interruption don't necessarily land on a buffer read boundary and that it could lead to the soundcard reading more than what was actually written, but that's potentially something that the sound system would be avoiding… I don't know.