32 bit float
Previously, we recommended purchasing the Zoom H5 as the preferred digital recorder for oral history recordings. But as with most technologies, recording technology continues to change, and with that the recommended recorder has changed.
If you’ve already bought a Zoom H5, you haven’t made a mistake. It is still an excellent choice for a portable digital recorder, but now there is a new breed of recorders using 32 bit float technology.
What does the bit rate mean?
Nearly all oral history associations around the world agree that the preferred recording format for oral history 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 set the recording level correctly.
The enormous dynamic range of a 32 bit float recording means that you do not have to set the recording level at all. Every recording will be recorded at the optimal level and can be adjusted later using a computer app without any 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 largest dynamic range of anything on earth between anechoic chamber (complete silence) and a massive shockwave is 210 dB, so a dynamic range of 1,528 dB available with 32 bit float technology means that all recordings will be captured with perfect quality without having to set recording levels.
In fact, the Zoom recorders with 32 bit float recording technology do not have any way to adjust recording levels because it’s not necessary.
The resulting file size of a 32 bit recording is about 1.3 times larger than a 24 bit recording, but that is a small price pay to not have to monitor recording levels.
Even when you record using 32 bit float technology, your edited and processed audio should still be saved as a 48 kHz 24 bit WAV file.