Why mono sounds are preferred over stereo sounds when it comes to analyse acoustic parameters like intensity, RMS amplitude, fundamental frequency etc

Question

In phonetic analyses, while using software like Praat, I have seen people's liking mono sounds over stereo sounds. Even if the recordings were done using a stereo microphone, the audio files are often converted to stereo. Any reason besides saving up a lot of memory? Thanks.

Answer 1

I've gathered a bunch of sources that marginally comment on whether to use mono or stereo audio. The consensus seems to be that mono audio saves space, like you said. However, a few of the sources note some of the times when you'd want to use stereo audio.

1. You want to record simultaneous electroglottograph data. Having both the audio and the electroglottograph data on one file as "stereo" audio keeps your data tidy.

2. You want to record audio once, but also want to choose the better half of the audio after your recording is done.

Also, note that human language is pretty much produced as a mono signal. I don't know of any human language that depends on stereo audio in order to communicate meaningful information. This link mentions that some occupations involving emergency communication make use of different audio in each ear to get more information across at the same time, but that's as close of a resource as I can find concerning stereo uses of language.

It also appears that Praat can't work with multiple files when they aren't all mono or all stereo, so that might also be a reason to use mono audio. Duplicating mono audio into both ears isn't quite the same as reducing stereo audio to mono audio.

Here's the most useful sources I found:

From https://colangpraat.wordpress.com/part-3-how-to-record-using-praat/

In the menu bar of the Objects window, click NEW and RECORD MONO SOUND. PRAAT also has the capability to record in stereo, but when it comes to gathering language data, mono files are preferred.

From https://web.stanford.edu/dept/linguistics/corpora/material/PRAAT_workshop_manual_v421.pdf

In most cases, you will record a single speech or voice sample and for that purpose you can select 'Record mono Sound..'. If you want to make stereo recordings, you obviously have to use “Record stereo Sound’. The latter option, for example, can be used to digitize the stereo output signal of the EG-2 PC Electroglottograph from Glottal Enterprises (http://www.glottal.com/electroglottograph.html), thus giving you access to a simultaneous recording of a speech and EGG signal.

From https://www.fon.hum.uva.nl/praat/manual/ExperimentMFC_2_2__The_stimuli.html

You can also use AIFF files, in which case stimulusFileNameTail would probably be ".aiff", or any other type of sound file that Praat supports. But all sound files must have the same number of channels (i.e. all mono or all stereo) and the same sampling frequency.

From https://www.fon.hum.uva.nl/david/LOT/sspbook.pdf

Before we go on, we repeat that a sound is represented in Praat as a matrix which means that sounds are stored as rows of numbers. A mono sound is a matrix with only one row and many columns. A stereo sound is a sound with two channels, each channel is represented in one row of the matrix. A stereo sound is therefore a matrix with two rows and both rows have the same number of columns. Each matrix cell contains one sample value. Whenever we want to use a formula on a sound we can think about a sound as a matrix.

From https://person2.sol.lu.se/SidneyWood/praate/monstee.html

But make sure you have something to gain from merging the channels into one mono signal. It is simpler to use the Stereo recorder in Praat and take the best channel.