The two most typical channel numbers for audio files/signals are mono (one channel) and stereo (two channels). Though the differences between the two are relatively easy to grasp, it may not be as simple to understand which is better in a given situation.
Is stereo or mono audio better? Stereo audio has 2 channels of information (left/right) and a more realistic sound with spatial panning across the left-right spectrum. Mono audio has one channel and a more direct sound. The overall audio quality (SNR, distortion, frequency response, etc.) is independent of stereo or mono formats.
In this article, we'll briefly discuss the differences between mono and stereo audio and dive into why mono is preferred over stereo in certain situations and vice versa in others.
Stereo Vs. Mono Audio
The main difference between stereo and mono is the number of channels used to record and playback audio signals. Stereo signals are recorded and played back with two audio channels (the left and right channels). Mono signals are recorded and played back with a single audio channel.
From a listener's perspective, the most noticeable difference is that mono signals cannot create a perception of width. Conversely, when played back through a stereo system (i.e., a stereo pair of speakers or a pair of headphones), stereo audio signals can produce perceived width.
Mono audio signals/files use only a single channel to convert signals into sound. Therefore, even if several speakers are connected, the same audio channel will drive all the speakers.
In the early days of audio, mono systems were used exclusively for radio broadcasts and even music records. However, in today's world, most music is in stereo and not mono.
As opposed to mono signals, stereo signals have two channels that get converted into sound. Hence, the signals sent to the left and right speakers are unique.
The playback systems which use two speakers are known as stereo systems. Stereo audio files contain both left and right channel information that commands the left and right speakers of the system to pull and push air.
Benefits Of Mono Audio
A majority of the listeners assume that stereo is an improvement over mono. However, there are numerous instances when stereo sounds come at a disadvantage.
In general, if a single source is recorded (especially in the case of a voice-over), the audio should be mono. There's no need to make the audio stereo unless for special/spatial effect(s).
Some of the benefits of mono audio are:
No Phantom Center
When both speakers play the same signal, your brain will think the sound source is positioned between the left and right speakers. It is known as the phantom mono source of the sound. For this reason, most interviews, Vlogs, podcasts, interviews, etc., are generally played using mono systems.
This phantom centre is largely based on psycho-acoustics and will change relative to the listener's position. Therefore, a mono recording has the benefit of not being overly “alterable” by the listener. Mono audio will sound more consistent on different systems and listening positions.
No Division Of Bitrate
If you export a sound file at 96 kbps, then upon playing it on stereo systems, the two channels will get 48 kbps each. However, if you play it on a mono system, the single channel will get the full 96 kbps. Thus, the sound quality of the file will be better.
Typical Audio Recordings In Mono
Typical mono audio recordings and applications include:
- Telecommunications (phone calls, video chat, etc.)
- Intercom systems
- Accessibility recording for those with hearing damage in one ear
- A small percentage of music
- Older playback systems with only one playback head
Benefits Of Stereo Audio
Stereo is the most common audio signal channel arrangement used in the music industry today.
Stereo audio is used because it gives a sense of realism and space to mixes (music, television, cinema, and more). We naturally hear in stereo since we have two ears, and stereo audio takes full advantage of this fact, offering the dimension of width to the audio.
With a host of benefits offered, stereo systems have successfully replaced mono systems. Some of the benefits are listed as follows:
Stereo became the ideal format for mixing music in the late 60s. As a result, most home audio systems and earphones make use of stereo signals. It also finds application in the PA systems used in concert halls. This is because of its ability to recreate the instruments' physical separation on stage.
Sound Localization & Width
Stereo systems create an impression of localization of the sound source. It refers to the ability of humans to identify the position of the source of the sound present within a space.
Say, for instance, you hear a drum playing; you will quickly determine the source of the sound and the position of the source. Most human beings can identify the sound source and its position with decent accuracy.
Similarly, you will easily perceive the audio played by a stereo signal to originate from two different sources of sound, namely the left and the right speakers. The differences between the channels of a stereo audio signal give us this enhanced sense of space.
The human brain uses numerous simple concepts to identify and localize sounds. Some of these concepts include sound wave pressure level, sound wave frequency, reverberation amount, dynamic range, and the timing difference between the audio entering your left and right ear.
These stereo systems aim to exploit the brain by creating an impression of sound source localization between the left and right speakers.
Typical Audio Recordings In Stereo
Typical stereo audio recordings and applications include:
- A large percentage of music
- Film, television and other video
- Broadcasting audio
- Binaural beats
Related article: Top 8 Best Stereo Miking Techniques (With Recommended Mics)
What About Surround Sound?
Surround sound, also known as multi-channel sound, is fairly self-explanatory. It is created by an array of different audio speakers placed behind and in front of the listener. The purpose of doing so is to surround the listener with audio signals to give the sense of, well, “surround sound.”
Surround signals can be recorded on DVD movies, DVD music discs, CDs, etc. These signals came into existence in the 70s, after the introduction of quad or quadraphonic sound. Since then, surround sound technology has evolved by leaps and bounds, and today, it finds application in numerous home theatres.
Surround sound can be produced using stereo signals as well. Upon looking at the waveform generated by a stereo audio file in a DAW (Digital Audio Workstation), you will notice that the file consists of two different waveforms. Each of the waveforms represents the two separate audio channels and thus gives rise to stereo sound.
Related article: Top 7 Best Digital Audio Workstations (DAWs) On The Market
These Stereo sound signals produce audio coming from different sound sources, and thus, they are used to produce the “surround sound” effect.
The human brain relies on the difference in the sound wave timing to understand the position of the sound source. According to our brain, the audio signals produced by a sound source present will reach our left ear faster than our right ear. The stereo signals use this concept to trick your brain and create a surround sound.
Related article: Top 4 Best Surround Sound Miking Techniques (With 3 Extras)
How can you tell whether an audio signal is mono or stereo? There are four methods to find out whether an audio signal/file is mono or stereo:
- File Info: Digital audio files will generally have imbedded info which can tell us if the audio has one, two or more channels. This method could give false results.
- Software: Check to see what your device is showing up as in your DAW.
- By Ear: Try to hear whether the left and right channels are exactly the same.
- By Phase Inversion: A neat trick to test whether a file is mono by inverting one of the channels.
Related article: How To Tell If An Audio Signal/File Is Mono Or Stereo
Are guitar amplifiers mono or stereo devices? Electric guitars and bass guitars are naturally mono instruments, so most guitar/bass amplifiers are mono as well, even if they drive more than one loudspeaker. However, some amplifiers are designed with stereo outputs to accommodate common stereo guitar/bass effects (chorus, delay, reverb, etc.).
Related article: Are Guitar & Bass Amplifiers Mono Or Stereo Devices?
Do microphones output mono or stereo signals? Microphones convert sound waves to audio signals via mic capsules. Most mics have one capsule that outputs one signal, making them mono devices. Some mics have multiple capsules and output multiple mono signals (which could be mixed in stereo). However, “stereo mics” are truly multiple-mono devices.
Related article: Do Microphones Output Mono Or Stereo Signals?