Understanding Bits, Samples, and Sound in Video Games

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What is a bit anyway? And how does it relate to sound in these machines?

A bit (short for binary digit) is the small unit of information a computer understands. A bit is often represented as either a 1 or 0, where one means “ON” and zero means “OFF.”

When a manufacturer writes about bits regarding processors, they are talking about the amount of information the CPU or GPU can manipulate at any given stage.

In other words, an 8-bit computer can process 8 bits at once. And a 16-bit computer can process 16 bits at once.

In the 1980s and 1990s, the transition to 16-bit from 8-bit meant a huge leap in terms of graphics and sound quality and overall processing speed.

Bits and sound quality

So how are bits connected to sound and sound quality?

Bear with me. This is going to be a bit technical. But I’ll try my best to explain it as simply as possible.

First, we must understand what sound is and how it is transformed from analog sound (fx our voice) into digital sound (in a computer) and back again.

And how it’s digitally created in a computer and transformed into something we can hear.

From analog to digital and back again

Analog to digital conversion and vice versa

Sound is waves traveling through some medium – most often air.

When we record our voice or an instrument into a microphone, the capsule in the microphone captures the sound waves and transforms these into analog electrical signals (measured in Volts).

These signals reach an Analog-to-Digital converter (AD converter) in our computer’s sound card and are transformed into bits the computer understands.

Likewise, when a sound has to leave the computer, it is converted from digital to analog via a Digital-to-Analog converter (DA converter). The electrical signals (measured in Volts) are then sent to the speakers, which push the air.

These airwaves are then picked up by our ears and translated into sound in our brains.

A sound wave can be illustrated by its amplitudes over time. The amount of oscillations of the wave over time is called the frequency and is measured in Hz.

Humans with perfect ears can hear between 20 Hz and 20 kHz. Most mid-aged adults can’t hear above 16Khz, which is why you shouldn’t fall for all the marketing when purchasing a pair of headphones.

A short note about Pulse Code Modulation

Pulse Code Modulation (PCM) is a method that is used to represent analog sampled signals digitally.

Every sample measures the signal’s amplitude (volume) at any given time.

An 8-bit signal has 256 (28 = 256) possible amplitude representations and ranges from -128 to +127.

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These 256 representations of the volume are called the bit depth.

In PCM current, each sample is quantized, so each sample is as close to the amplitude and frequency of the sound wave. You can view these as digital steps.

An 8-bit sound wave will have more digital artifacts than a 16-bit sound wave.

These artifacts helped establish the 8-bit aesthetic we know and love from the Commodore 64 SID chip and the Nintendo Game Boy.

Using software plugins such as bit crushers, established artists such as Björk and many within the IDM scene have used the 8-bit sounds as a creative musical choice even though they could easily reproduce music with higher fidelity.

Sample rate and bit depth

Now take a look at the illustration I’ve created below, which illustrates how an analog sound wave (blue) is reproduced in the digital domain (quantized purple wave):

Sample rate and bit depth video games explained
On the left side, the digital reproduction of the analog sound wave is less precise than on the right side. This is because both the sample rate and bit depth are lower. As a result, you’ll hear more digital artifacts.

The horizontal axis is the sample rate (or sample frequency), meaning how many times the amplitude of the sound wave is measured per second. The sample rate is measured in Hz or kHz (fx 44.1 kHz).

The higher the sample rate, the more accurate the measurement of the sound wave is.

The vertical axis is the bit depth, meaning the number of possible volume levels at which the sound wave can be measured.

The higher the bit depth, the more accurate the measurement of the volume (amplitude) of the sound wave is.

Aliasing, which can be heard as digital artifacts, is created when the interval between two samples (the sample rate/frequency) isn’t small enough to accurately measure the number of oscillations over time (the frequency measured in Hz).

Because there are more wave oscillations at higher frequencies, digital artifacts are first heard at higher tones than at lower, more bassy tones.

In closing

I hope this short article helped provide a basic understanding of bits and their connection to sound so that when you read about 8-bit machines such as the Nintendo NES, Commodore 64, or Nintendo Gameboy, or 16-bit machines such as the Nintendo SNES or Commodore Amiga 500, you’ll have a better understanding of what this means.

Until next time, happy gaming!


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ABOUT THE AUTHOR:

Jan has played video games since the early 1980s. He loves getting immersed in video games as a way to take his mind off stuff when the outside world gets too scary. A lifelong gamer, the big interest led to a job as a lecturer on game sound at the University of Copenhagen and several written articles on video games for magazines.

Read more on the About Page.