What is sample rate? It is how many times per second an audio signal is measured, in hertz. A higher rate captures higher pitches. 16 kHz is common for speech and 44.1 kHz for music. Each measurement is one sample, so a higher rate also means more data per minute.
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Files up to 2 GB · export to TXT, MD, DOCX, PDF, SRT and VTT · speaker labels and timestamps · about 30 languages
Key facts
- A recording holds pitches up to half its sample rate, so 16 kHz covers sound up to 8 kHz, which includes most of the human voice.
- Voice calls often use narrower rates than music, which is why a phone call sounds duller than a studio recording.
- Raising the rate of an existing file adds no detail; it only repeats what was already captured and makes the file larger.
- Uncompressed mono at 16 kHz and 16 bits takes 32000 bytes per second, which is about 1.9 MB a minute.
- Sample rate is not bitrate: the first counts measurements per second, the second counts bits of data per second after any compression.
What it looks like
// read the rate of a file
ffprobe -hide_banner talk.wav
// Stream #0:0: Audio: pcm_s16le, 44100 Hz, stereo
// make a 16 kHz mono copy for speech
ffmpeg -i talk.wav -ar 16000 -ac 1 talk_16k.wav
// size per second: 16000 samples x 2 bytes x 1 channel = 32000 bytes
More
See the full list of languages, the tools and the glossary.
Frequently asked questions
Which sample rate is best for speech?
For speech, 16 kHz is common and enough. Music uses 44.1 kHz or more to reach the highest pitches, which a voice does not need.
Should I convert my recording to 16 kHz before sending?
Not required. Send it as it is. Lowering the rate is only useful to make a very large file smaller.
Does a higher sample rate improve a transcript?
Not beyond a point. Speech content sits well below 8 kHz, so clear speech and low noise help much more than extra rate.
What happens if the rate is too low?
High-pitched sounds such as the letter s and t are lost, and speech sounds dull and muffled, so words are easier to confuse.
Where do I find the rate of my file?
Run ffprobe on it or open its properties in a media player. The audio stream line shows the rate in Hz next to the channels.
Sources
Each source was opened by hand on the date shown. Pages change, so open the source if a detail matters to you.
- Sampling (signal processing) (Wikipedia), Wikipedia · checked
- Bit rate (Wikipedia), Wikipedia · checked
Try it on your own recording
Send your voice message, audio or video to @potok_now_bot on Telegram and the text comes back in the chat.
Open @potok_now_bot in Telegram