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# Audio Sampling Rate

The sampling rate is the rate at which an audio signal is sampled and digitized. In general, the higher the sampling rate, the more information is preserved in the audio signal. This table lists commonly used sampling rates.

Sampling rate (Hz) | Use
--- | ---
8,000 | Telephone; adequate for human speech but without sibilance; ‘ess’ sounds like ‘eff’ (/s/, /f/).
11,025 | One quarter the sampling rate of audio CDs; used for lower-quality PCM and MPEG audio, and for audio analysis of subwoofer bandpasses.
16,000 | Wideband frequency extension over standard telephone narrowband 8,000 Hz. Used in most modern VoIP and VVoIP communication products.
22,050 | One half the sampling rate of audio CDs; used for lower-quality PCM and MPEG audio.
32,000 | MiniDV digital video camcorder, video tapes with extra channels of audio (for example, DVCAM with 4 Channels of audio), DAT (LP mode), NICAM digital audio, used alongside analog television sound in some countries. Suitable for digitizing FM radio.
44,056 | Used by digital audio locked to NTSC color video signals (245 lines by 3 samples by 59.94 fields per second = 29.97 frames per second).
44,100 | Audio CD, also most commonly used with MPEG-1 audio (VCD, SVCD, MP3). Much professional audio equipment uses (or is able to select) 44,100 Hz sampling, including mixers, EQs, compressors, reverb, crossovers, recording devices.

Streamed audio must have a sampling rate of either 8,000 Hz (8 kHz) or 16,000 Hz (16 kHz).

If FFmpeg is enabled, HPE IDOL Speech Server accepts audio files with a range of sampling rates. HPE recommends that the sampling rates are at least the sampling rate required by the processing task. Audio with sampling frequencies below this are upsampled, which causes severe quality issues. The minimum sampling frequencies are 8 kHz for processing telephony audio and 16 kHz for processing broadcast audio.

The audio bandwidth can restrict whether you can sample an audio file at 8 kHz or 16 kHz. For more information, see Audio Bandwidth.

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