32 bit float

32 bit float is a recording technology with a high dynamic range (the difference between the softest and loudest recording) impacting the need to adjust or monitor recording levels. It has been used by the sound industry particularly with film and video for years.
Oral History NSW anticipates this recording technology may also eventually be used in the field of oral history. Existing digital recorders capable of recording 28 bit 48kHz WAV file continue to be suitable and recommended for archival quality oral history recordings as per international guidelines. See: iASA - Field Recording Standards

What does the bit rate mean?

The archival recording standard for audio recordings is a WAV file sampled at 48 kHz with a resolution of 24 bit.
In simple terms that means that audio is sampled 48,000 times per second, and the audio signal is given a number (amplitude value) between 1 and 16,777,216. In terms of decibels, this gives a recording dynamic range of 144 decibels (dB). With a 24 bit recorder, the recording level must be set correctly. If the recording level is too loud, the audio will be distorted, because it will be at a level that cannot be defined. A recording that is too quiet can be made louder using a computer app, but the level of unwanted noise will also be increased as the wanted audio level is increased. 24 bit recording is much more tolerant of low level recording than a 16 bit recording, but it is still important to understand your equipment and set the recording level correctly.

The increased dynamic range of a 32 bit float recording means recordings levels do not need to be set and recordings can be adjusted later using a computer app without loss of quality.

Sample Resolution	Number of possible amplitude values	Dynamic Range	Stereo WAV file size per hour of audio
16 bit	65,536	96 dB	659 MB
24 bit	16,777,216	144 dB	988 MB
32 bit integer	4,294,967,296	192 dB	1,310 MB
32 bit float	4,294,967,296	1,528 dB	1,310 MB

The resulting file size of a 32 bit recording will be approximately 1.3 times larger than a standard 24 bit recording.
Even when recording using 32 bit float technology, edited and processed audio should still be saved as a 48 kHz 24 bit WAV file.
If you are commisioned to record interviews, particularly for a library or collecting archive, be sure to consult first to confirm any technical specifications, digital recorders, and file formats and outputs.

See also: