Wrap your head around a totally new way to record audio

Wrap your head around a totally new way to record audio

Frank Beacham March 10, 2024

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Most of us who have long recorded audio for video have developed a tried-and-true workflow. We don't always get perfect sound, but we have the learned the rules of how stay out of trouble. One of the key tricks is to ride the levels correctly so we don't overload the audio levels.

There's a new technology that turns this rule on its head. It's called 32-bit float recording. In essence, it makes critical gain riding a thing of the past. The recordist always achieves excellent audio levels without the pressure of riding the gain in the field.

This is not market-speak for a re-birth of old technology. It is not a form of auto gain (AGC) or older problematic automatic gain riding from a previous era. There no odd artifacts in the sound.

Quite simply, it is made possible due to the increased power of computing in small devices. In a 32-bit float recorder, you have two high-performance ADCs (analog-to-digital converters) working in tandem to create a single audio file. One ADC attacks the lower gain and the other attacks the higher gain. If one chip overloads, the other ADC handles it.

Zoom R4 MultiTrak 32-Bit Float Recorder

Fluctuating dynamics have always proved challenging when trying to ensure consistent audio levels in the field. Loud sounds coming out of the blue can cause unexpected clipping. Very quiet sounds can easily get lost in the noise. This is especially true for film and documentary crews recording wild outdoor sounds.

However, the challenge can be just as difficult for single-person journalists or music recordists who have to do multiple tasks at once. As a reporter, I have always recorded interviews. And since day one, I've been preoccupied about getting good levels even to the point of being distracted from the subject's words in interviews.

Fortunately, those days are now over. I just start the recorder and the level is always correct. There are no level settings to worry about. I can concentrate on the subject matter and not the technical issues. That, alone, is a gamechanger.

Recorders with 32-bit float capability are now flooding the market. Zoom was first with their F6, F3 and F8N Pro recorders. Then came the M2 and M4 MicTrak. The new Zoom R4 MultiTrak four-channel model sells for only $199. Sound Devices moved to 32-bit float with their MixPre II series of recorders. Tascam has introduced its first 32-bit float models, the Portacapture X6 and X8 models.

Sound Devices Mix Pre 10 II Audio Recorder

The recording quality on 96 kHz/32-bit float recording technology means that you can capture audio softer or louder than ideal. When using a tiny two-channel Zoom F3 set to simultaneously record in both standard 24-bit WAV and 32-bit float mode, all I see is a tiny waveform of the audio on the display and a red recording light. There are no adjustments for sound levels.

Doing a simple test with the free Audacity DAW, I accessed a normalized 32-bit float recording and then saved it to standard WAVE file. If it was too soft, I raised the level. If it was too loud, I lowered it. The process is flawless and simple.

Most major DAWs and video apps now support 32-bit float audio, including the latest versions of the free Audacity DAW, Avid's Pro Tools, Adobe Premiere Pro, DaVinci Resolve, Cubase and Apple's GarageBand, Logic Pro, iMovie and Final Cut Pro.

Tascam Portacapture X8 8-Channel 32-bit Float Portable Audio Field Recorder

With 32-bit float, files are encoded into an IEEE-754 format. This includes one bit for positive or negative; eight bit exponent and 23 bit fraction. When viewed in decibels, that's a range of 1528 dB.

Since the greatest difference in sound pressure heard on the planet can be about 210 dB, from anechoic chamber to massive shockwave, 1528 dB is far beyond what will ever be required to represent sound in a computer file.

Employing 32-bit float takes a little getting used to. The recorded levels may appear to be either very low or very high while recording, but they are easily scaled after recording by the DAW software with no additional noise or distortion. Once the user trusts it, confidence quickly builds.

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There are a couple of caveats when using 32 bit float. All 32-bit files are about 33 percent larger than standard 24-bit files. This might require a larger SD card for longer recordings.

There is one other aspect of 32-bit float files which is not immediately obvious. Files recorded with 32-bit float record sound where 0 dBFS of the 32-bit file lines up with 0 dBFS of the 24- or 16-bit file. Keep in mind that unlike the 24- or 16-bit files, the 32-bit file goes up to +770 dBFS. So compared to a 24-bit WAV file, the 32-bit float WAV file has 770 dB more headroom.

When recording 32-bit float audio files, use the best audio electronics possible. Avoid cheap microphones which can easily overload. With top level pro gear, very loud, unexpected sounds can be captured without the use of limiters.

32-bit float is radical advance in audio recording. From journalists working one-man-band to boom operators on feature films, the days of digital clipping and lost takes are over. The precise setting of the trim and fader gain is no longer an issue. The sound is good no matter where the levels are set. Fewer sound operators are often needed on a set. This may be the breakthrough audio technology of the new century.

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