When espeak_Initialize is called with a large buffer size, I get more pops than usual. This also occurs when sending the output to an audio file. Example code:

#include <string.h>
#include <espeak-ng/speak_lib.h>

int main() {
	char data[] = "/tank/home/tyler/misc/homes-backup";
	int len = strlen(data);
	espeak_Initialize(AUDIO_OUTPUT_SYNCH_PLAYBACK, 3000, NULL, 0);
	espeak_SetParameter(espeakRATE, 390, 0);
	espeak_Synth(data, len + 1, 0, POS_CHARACTER, 0, espeakCHARS_UTF8, NULL, NULL);
	return 0;
}

With this string, the pop is right on the b of backup. If I change the buffer size to 1000, it disappears.