Understanding Audio Bit Depth: 8-bit vs. 16-bit vs. 24-bit

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Understanding Audio Bit Depth: 8-bit vs. 16-bit vs. 24-bit

When it comes to digital audio, one of the most critical factors in determining the quality of a recording is the audio bit depth. In this article, we’ll delve into the technical details of audio bit depth and explore the differences between 8-bit, 16-bit, and 24-bit audio recordings.

Bit Depth

What is Audio Bit Depth?

In digital audio, sound waves are converted into a series of numerical values that can be stored and manipulated by computers. Audio bit depth refers to the number of bits of information used to represent each sample in a digital audio recording. Each sample represents the amplitude of the sound wave at a specific point in time.

The bit depth determines the range of possible values for each sample. For example, an 8-bit audio recording has 256 possible values, while a 16-bit recording has 65,536 possible values, and a 24-bit recording has over 16 million possible values. This increase in possible values provides greater resolution and accuracy, resulting in improved sound quality.

Dynamic Range

Another critical aspect of audio bit depth is dynamic range, which refers to the difference between the quietest and loudest sounds that can be recorded. With an increase in bit depth, the dynamic range of a recording also increases. For example, a 16-bit audio recording has a dynamic range of 96 dB, whereas a 24-bit recording has a dynamic range of 144 dB. This difference in dynamic range is quite significant and is one of the reasons why 24-bit audio is preferred for professional applications.

Quantization Noise

Quantization noise is an inherent part of digital audio and is introduced during the process of converting an analog audio signal to a digital representation. Quantization noise is essentially the difference between the actual analog signal and the closest quantized digital value. The more bits used for quantization, the lower the level of quantization noise.

However, as the bit depth increases, the noise introduced becomes less of an issue. At 16 bits, quantization noise is typically not audible, but it can become noticeable when processing audio. At 24 bits, quantization noise is virtually non-existent, even when processing audio.

Conclusion

In conclusion, audio bit depth plays a crucial role in the quality of digital audio recordings. Increasing the bit depth of an audio recording provides greater resolution and accuracy, resulting in improved sound quality. Professionals in the music industry typically prefer 24-bit audio due to its higher dynamic range and lower quantization noise. However, for most consumer applications, 16-bit audio is perfectly adequate and results in high-quality sound.

It is also important to note that bit depth is just one aspect of digital audio quality. Other factors such as sample rate and compression algorithms also play a significant role in determining the overall quality of a digital audio recording. Nonetheless, understanding audio bit depth is a crucial step in the journey to becoming a proficient audio engineer or producer.

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Bit depth, an important factor almost unknown

Very often we see people talking about topics that are important, like bitrate for example. Most of the time without understanding exactly what that means. Sometimes they even do trial and error and for various reasons it may be that the result they obtain is misleading, since they are not considering that modifying the bitrate without looking at the sample rate and the bit depth, is to act blindly and therefore the Results will always be misleading and we should not draw definitive conclusions from them.

We have detected that many people instead of giving a reading that allows them to understand what bitrate, sample rate or bit depth are, prefer to manipulate them without understanding them and, based on the result of one or two songs, they often reach conclusions. wrong about what is the right combination.

Bitrate

It is bitrate It is the amount of information that passes per second, that is, the amount of detail that an audio file can contain in a video. The bigger the bitrate means what will be passing more information per second; therefore the file will be bigger but it will contain more details, which will give it a higher quality. We will put an example to understand it very easily. Images that we have a great draftsman or painter and that we ask him to make a portrait of a person but we tell him that I can only use 5 colors and he cannot mix them.

As a result we will obtain practically a caricature and not a portrait itself. In other words, it will have less quality if we understand quality to be a faithful copy of the original.+

On the other hand, if that same painter asks you to make a portrait, but we stop using the entire color palette, you will be able to make a very realistic portrait, of very high quality, very faithful to the original.

Why did this happen? Because it contains much more information. There are many more shades. That explains exactly how bitrate affects the quality of a video or audio file.

Sample rate

When we record a video, for example, it is as if we were taking a series of photographs and then quickly saw them one after the other and that would give us the illusion of movement. In exactly the same way that cartoons worked in ancient times. Obviously if we only use three drawings per second the quality of the cartoon will be very low because you will see a series of jumps and not an action continues. If instead we use 24 drawings per second we will see a very high quality cartoon where we will seem to see an action continue without any Jump.

The sample rate is the number of samples per second that are taken to form a video or an audio file. Audio on a professional CD uses 44100 samples per second. If we lower that quantity we will notice a loss of quality and if we increase it to more than 44100 samples we will be able to obtain a very high quality HD.

Bit depth

The bit depth determines how many “steps” the curve or wave will contain that will contain our audio or video file. Obviously, the more steps the wave pattern has, it will be more faithful and, on the contrary, if it contains few steps, the wave pattern will be very rough.

So here we are understanding the importance of bit depth that for example in music affects even the dynamics of music. That is, how much can the volume of an instrument rise and fall in different passages. At different bit depth rates we will obtain different levels of decibels

Bit Depth explanation

Definition

In digital audio, the bit depth is the number of information bits of each sample and is closely linked to the resolution of the audio. Unlike an analog signal, which is periodic and is composed of infinite points, digital audio is a discrete signal since it is composed of a finite number of points. Use binary numbers (bits) to determine the number of available states to represent the strength of each audio sample and thus represent the signal. “The quality of the representation increases, in general, when this number of states is increased. For example, […] high-fidelity music recording is obtained on a CD with 65,536 amplitude levels. The number of possible states of a binary system of n digits (n bits) is E = 2 ^ n. ” 1. In summary, it is the resolution, in terms of amplitude, that will have a digitized signal. Determine the dynamic range of that signal. In the following image we can see how a signal is represented in 4 bits of depth. 4 bits generate 16 possible values on the vertical axis.

Aspects to consider

The accuracy of each sample is determined by its bit depth. Then, the higher the bit depth, the higher the resolution in the digitized signal. In addition, the greater the bit depth, the greater the dynamic range for the signal because it will have more points to represent the amplitude of each audio sample. It follows that low levels of bit depth can affect the shape of the wave and thus not achieve a good representation of the original wave because there are fewer possible points to represent it. For example, in the following graph we can see a sinusoid represented with different bit depths. A depth of 1 bit will generate a wave more similar to the square wave (depending on the quantification) because we only have two possible points on the vertical axis.

Requirements

A very important aspect to keep in mind is that at greater bit depth we will need more resources to process the audio and more memory to save it. This is because we will have more information. The size of our audio file will be given by the following account:

Bit number * Sample rate * number of seconds duration [* 2 (if stereo signal)]

Then, for example, the size of a second of audio on a CD, which works with a depth of 16 bits and a sampling frequency of 44,100Hz / second will be given by the following account:

1 second = 16 * 44100 * 2 (since it is stereo)

1 second = 1411200 bits (0.1764 Mb)

Sample Rate and Bit Depth

In sound and audio software and hardware specifications we are often told about processing capacities of up to 96kHz and 64bit operation, but what do these issues really mean? And how do they affect the quality of our sound?

Sample Rate and Frequency Range

The sampling rate is the frequency with which the A / D converter (analog to digital) measures the levels of a signal, the samples are broadly analogous to a series of snapshots. If the converter takes ten samples of the signal every second, it would have a sampling rate of 10 Hz.
The frequency range that an A / D converter (present on a sound card for example) can capture is determined by the sampling frequency, or sampling rate. However, in this there is a strict law that may seem unintuitive: the maximum frequency that can be captured is only half of the sampling frequency. A sampling rate of 10 Hz can capture a maximum frequency of 5 Hz, not 10 Hz. The reason is that, without double the samples of a sound source, some of the oscillations of the signal are lost.
But what happens if there are frequencies higher than the capacity of our sampling frequency in the captured analog audio signal? Aliasing then occurs, phenomena that occur when the highest sampling frequency that has been sampled is higher than the frequencies that can be accurately captured by the A / D converter. Aliasing adds distortion to the audio signal artificially, adding lower frequencies to higher partials. Aliasing can occur in a digital audio system as a result of a poorly designed A / D converter, but you are much more likely to hear it when you play high notes from a software-based synthesizer. If the synthesizer does not use an antialiasing technology, the high notes have the possibility of becoming random groups of tones that have no relation to the key note you are playing.

The researchers at Bell Laboratory are familiar with this problem since 1920 and conceptualized the principle as the Nyquist-Shannon sampling theorem. The theorem is simple: to sample the frequency value of x correctly, you need a sampling frequency of at least twice x. (The maximum frequency at which it can be sampled without aliasing at a certain sampling rate is thus the so-called Nyquist frequency.) So why do we need the sampling rate to be twice as fast as the most frequency? high to be recorded? Because each ordinary period of a waveform includes an upward and a downward oscillation. If the A / D converter takes less than two samples per period, it cannot capture the entire oscillation. In order to capture each “up” and “down” state, you need to take at least two samples from each period. Thus, the sampling rate has to be twice the highest frequency that must be recorded.

According to the Nyquist-Shannon theorem, to sample frequencies that are in the upper limit of the human ear (around 22000 Hz), you need a sampling frequency of around 44000 Hz, which is, not by chance, the rate Normal sampling for commercial audio CDs, 44100 Hz.

This obviously allows you to sample the frequencies from the top of the range of our ear, but what happens when the frequencies of the signal that reach the A / D converter exceed the maximum frequency limit of 22 kHz? They fold into the audible spectrum as distortion, so the A / D converters incorporate an anti-aliasing filter that eliminates these high partials, before the audio is converted to digital format.

AUDIO WHY SEND MY WAV FILES TO 16 BITS, 44,100HZ?

Many will ask, what do we mean by the technical term of 44,100Hz at 16 bits? That term refers to the coding standard with which the compact disc was marketed in the 80’s.

The quality of a compact disc has a depth (bit depth) of 16 bits and a sampling rate of 44.1 kHz, which means that it is the standard quality with which your music will be played from the physical format. But what is the depth and frequency of sampling? Why not handle a higher quality coding such as 24-bit at 96kHz?

Bit depth:

In digital audio using pulse code modulation (MIC or PCM by Pulse Code Modulation), it is the number of bits of information for each sampling and corresponds directly to the resolution of each sampling. Examples of this: The compact disc which uses 16 bits per sampling, DVD Audio and Blu Ray which support 24 bits per sampling. Bit depth is only applicable to lossless (loseless) files and not to compressed (lossy) files such as mp3, wma, etc. With 16-bit audio, there are 65,536 possible levels. With all the higher resolution bits, the number of levels is doubled. By the time we reach 24 bits, we actually have 16777216 levels. Remember that we are talking about a frozen audio segment in an instant of time.

Sample depth:

Pulse code modulation (MIC or PCM by Pulse Code Modulation) is a modulation procedure used to transform an analog signal into a bit sequence. The unit of measure commonly used is Hertz (Hz).

When it is necessary to capture the entire range of human ear capacity (20-20,000 Hz) such as recording studio music, or various types of acoustic events, audio waves are usually recorded at 44,100 Hz, 48,000 Hz, 88,200 Hz or 96,000 Hz. Sampling frequencies of more than 50,000 Hz or 60,000 Hz do not provide useful information to human ears, although the difference is small, in 96,000 Hz sampling it is effective eliminating distortion.

Why send my WAV files at 16 bits, 44,100Hz?

To hear the difference between your music in 16 bits at 44,100Hz and 24bits 96,000Hz you must have a decent professional audio system or professional headphones, have a well-trained ear and this without counting the noise or noise that exists around you, However, if you want to compare both formats, the difference is imperceptible in low-end headphones, speakers of a stereo coppel or the speakers of your macintosh.

It also greatly influences the mixing and production made during the recordings by the audio engineer when capturing the instruments in their raw state. This greatly influences your WAV files to be heard well in their final mix at 44.1KhZ 16 bits or 96kHz at 24 bits.

The society of audio engineers recommend 48,000 Hz for most applications however they give recognition to 44,1000 Hz for the compact disc and its various applications. In any case, it is recommended for its average consumption in digital media a coding at 44,100 Hz at 16 bits to make up your music in a compact disc format and also for digital distributions … although spotify, itunes, etc … compress your music in mp3 format to 128kbps, a minimum and lousy quality.

WAV is a lossless digital audio format (loseless) and are raw audio files which you can request from your audio engineer at no cost when you finish mixing your tracks.