单语范例（未经PONS编辑处理）
Usually, the blasts use frequencies between 30 and 150 Hz, which also helps stop the signal from weakening too much.
en.wikipedia.org The top of the minute is marked by a 0.5 second 800 Hz tone.
en.wikipedia.org The lowest frequency that has been identified as a musical tone is 12 Hz under ideal laboratory conditions.
en.wikipedia.org An even parity bit follows, then a stop bit at 1200 Hz.
en.wikipedia.org They used 1600 Hz tones as the standard stimuli, while a 900 Hz tone represented the rare target stimuli.
en.wikipedia.org