STEREO VS. MONO: DIFFERENCES & COMPARISON

Stereo and mono sound are differentiated by the number of channels utilized to record and play music. The number of channels is always the same. A single audio channel is used to capture and play the mono signal, whereas a two-channel audio system is used to collect and play stereo sounds. As a listener, the most noticeable distinction is that stereo sounds can create the illusion of depth, whereas non-mono sounds cannot. The distinct sound is determined by the number of channels utilized to record and reproduce speech.

AUDIO FILES

Stereo systems are playback systems that make use of two speakers. Stereo audio files such as stereo MP3 and WAV files provide material on the left channel and right channels that tell you to push and pull air to the right and left speakers.

You also saw that there are two waveforms separate from the file if you’ve ever looked up a stereo audio file inside a digital audio (DAW) workstation. A single audio channel is represented by each waveform.

Figure 1: A stereo audio file.

Mono audio files only contain a single audio channel.

Figure 2: A mono audio file.

Mono vs. Stereo Playback

Stereo systems may create the impression of sound source localization. The ability of humans to identify the location of a sound source within a space is referred to as sound source localization.

For example, if you hear a dog barking, you can usually tell the way the sound is coming from and how far away the sound the dog)is. And with their eyes closed, most people should be able to pinpoint sounds with reasonable precision.

It makes sense that you would interpret the sound emitted by a stereo system as coming from two distinct sound sources may seem that it’s emanating from two opposite sources in some of these cases but not necessarily.

Figure 3: Sound playing from two speakers.

Since it uses basic ideas to locate sounds, the human brain is easily duped. These concepts include timing differences between sounds to the left and right ear, frequency of the sound wave, sound wave pressure, dynamic range, and amount of reverberation.

Stereo devices take advantage of the brain’s gullibility to create the “impression” of sound source localization between the system’s left and right speakers.

When the left and right speakers play the same signal, for example, you can interpret the source of the sound to be immediately behind the speakers; this is known as a phantom mono sound source since the actual sound sources (the speakers) are located to the sides.

Figure 4: Two speakers creating a phantom mono sound source.

To determine the left/right positioning of a signal, the brain uses variations in sound wave timing. Sound waves from a sound source closer to your left ear will enter your left ear before reaching your right ear. Even if the timing variations are minor, they assist your brain in locating the sound.

Figure 5: Sound waves traveling a shorter distance to reach a person’s left ear than a person’s right ear, creating a delay.

When you replicate this process with a second speaker and feed the same stimulus to both speakers, the brain believes the sound source is in front of you.

Figure 6: A stereo playback system creating the impression of sound source localization.

When variations are added to one of the signals, the sound produced is believed to be wider.

Width (X-axis) is only one of three measurements that can be perceived using a stereo device. Height (Y-axis) and depth (Z-axis) are the other measurements. These three dimensions combine to form a 3-D space known as a stereo image.

Use a pair of headphones or a stereo playback device to listen to the audio in the following clips. If you want to use a stereo playback machine, make sure your head is in an equilateral triangle with the headphones. Your speakers should be angled 45 degrees toward you to guarantee that you perceive the stereo image accurately.

The height at which you hear the sound within a stereo field is determined by frequency. High-frequency signals are located above low-frequency sounds. Hi-hats in a song, for example, can sound as if they are placed above the bass guitar.

The relative height, dynamic range, and reverberation amount of a sound all influence its depth. Sounds with a low level and a small dynamic range, as well as sounds with a lot of reverb, are pushed to the back of the stereo sector.

Mono playback systems have only one speaker and can only produce a two-dimensional image of depth and height. To create the directional timing variations that your brain uses to understand the width, you’ll need two speakers.

Mono vs. Stereo Recording

A single channel of audio is captured while a single microphone is monitoring a sound source. A single speaker or a pair of speakers could be used to playback a mono recording like this.

Figure 7: A guitar being recorded in mono.

As mono sounds are playing back into a stereo system, they are converted to dual-mono. The audio from a single channel is duplicated and sent to the left and right speakers.

Two microphones are needed to obtain true stereo recordings. You’ll need to pan one of the microphone recordings to the left and the other to the right while processing a stereo recording.

Figure 8: A guitar being recorded in stereo.

A back-to-back contrast between a mono guitar recording and a stereo guitar recording can be seen in Steven Law’s video below. The X-Y technique is the stereo microphone technique he’s using; it produces a relatively large stereo picture that’s still mono-compatible. By angling the microphones further outward or using different acoustic guitar recording techniques, you can obtain an even wider stereo shot.

Many handheld recorders have the capacity to record in stereo, using a pair of built-in microphones to capture sound. The left microphone’s information is saved to the left channel of the saved audio file, while the right microphone’s information is saved to the right channel. The Zoom H4N Pro has two microphones and can record in stereo mode.

Figure 9: A Zoom H4N Pro handheld recorder.

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