32-Bit Float Files Promise A Revolution In Field Recording

Sound Devices has upgraded its MixPre line of portable audio mixer/recorders and Zoom will soon deliver its F6 mixer/recorder. Both have a revolutionary new feature: so much headroom that it no longer matters where the gain level is set during recording. Both explosive high and quiet volume signals can be recorded at full audio quality without touching a control.

That is a major advance for field recordists: basically hands free gain riding. With these recorders, clipping is impossible, regardless of audio levels. Both the Sound Devices and Zoom recorders introduce the ability to record 32-bit floating point WAV files. The primary benefit of these files is their ability to record signals exceeding 0 dBFS. There is in fact so much headroom that from a fidelity standpoint, it doesn’t matter where gains are set while recording.

Zoom F6.

Zoom F6.

The idea of 32-bit floating point recording is very new and a bit technical to explain. But to sound operators, at a price beginning at about $650, the good news is you can buy a mixer/recorder that allows risk free level riding. Like everything, there is a trade off. The 32-bit floating point files are about 50 percent larger than standard 24 bit audio files. Some good news is audio levels in the 32-bit float WAV file can be adjusted up or down after recording with most major DAW software with no added noise or distortion.

So what is the difference between 16-bit fixed point, 24-bit fixed point and 32-bit floating point files? Sound Devices explained in a white paper.

Traditional 16-bit WAV files store uncompressed audio samples, where each sample is represented by a binary number with 16 digits (binary digit = “bit”). These numbers are “fixed-point,” because they are whole numbers with no decimal point. Numeric values represent a discrete voltage level corresponding to the signal amplitude.

Illustration courtesy of Sound Devices.

Illustration courtesy of Sound Devices.

The number 65535 represents the maximum amplitude (loudest) the signal can be, and the lowest values represent the noise floor of the file, the lowest bit toggling between 0 and 1. The maximum dynamic range that can be represented by a 16 bit WAV file is (0 dB – (-96.3 dB)) = 96.3 dB. Moving to 24-bits (fixed point) WAV files improves on the amplitude resolution of 16-bit by extending the 16-bit word, adding 50 percent more bits, to make a 24-bit word.

Compared to fixed-point files (16- or 24-bit), 32-bit float files store numbers in a floating-point format. This is fundamentally different than fixed point, because numbers in these WAV files are stored using decimal points and exponents. This difference is significant because much larger and smaller numbers can be represented compared to a fixed-point representation.

The first bit indicates a positive or negative value, the next eight bits indicate the exponent and the last 23 bits indicate the mantissa, or the part of the algorithm that follows a decimal point. The dynamic range that can be represented by a 32-bit (floating point) file is 1528 dB. Since the greatest difference in sound pressure on earth can be about 210 dB, from anechoic chamber to massive shockwave, 1528 dB is far beyond what will ever be required to represent acoustical sound amplitude in a computer file.

Most modern DAW software can read 32-bit float files. When a DAW first reads a 32-bit file, signals greater than 0 dBFS may first appear clipped since, by default, files are read in with 0 dB of gain applied. By applying attenuation to the file in the DAW, signals above 0 dBFS can be brought below 0 dBFS, undistorted and used just like any 24- or 16-bit file.

MixPre 3.

MixPre 3.

For 32-bit float recording, exact setting of the trim and fader gain while recording is no longer a worry. The recorded levels may appear to be either very low or very high while recording, but they can easily be scaled after recording by the DAW software with no additional noise or distortion.

Recording 32-bit float audio files, along with high performance analog and digital electronics that can take advantage of its massive dynamic range, offer sound designers and sound mixers a new way to record audio. This is especially useful for applications where very loud, unexpected sounds can be captured without the use of limiters.

This is a remarkable new advance in mobile recording technology. 

Let us know what you think…

Log-in or Register for free to post comments…

You might also like...

IBC 2019 Cloudy, Streaming and 8K

In this thought-provoking missive, Gary Olson delivers his predictions and insights for IBC 2019.

Secure IP Infrastructures For Broadcasters - Part 1 - Secure Servers

In this series of three articles, we investigate the underlying aspects of computer server design for high value security and 24-hour operation. In the first article we look at advanced server security, in the second article we understand how servers…

ZombieLoad And Other Things That Go Bump In The Night

May 14, 2019 may not have seemed a particularly important date for those who edit and color grade on Mac’s and PC’s. But it was. By chance, that day I went looking for the May Windows 10 Feature Update (1903). I was sur…

The Move Towards Next Generation Platforms

Whenever I’m asked about my opinion on the transition to IP, I always state that the impact can’t be appreciated until its history is understood. This brings into context the need for broadcasters to educate and surround themselves wit…

Essential Guide: Immersive Audio Pt 3 - Immersive Audio Objects

Immersive audio transforms the listening environment to deliver a mesmerizing and captivating experience for a wide range of audiences and expansive group of genres.