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When it comes to audio quality, it can be a bit difficult to understand everything that is going on. People use different terms to define an audio file, and the worst part is that companies usually don’t explain when they apply this audio jargon to their products.
Two terms that we often come across are shallow and sampling rate. These are two common terms we see when we look at the properties of an audio file. It’s important to know what they mean and how they affect audio quality, so let’s take a look at what these terms mean.
What is the sampling rate?
Digital images are made up of pixels, tiny bits of color data that combine to form a cohesive image. Think of a digital audio file as a digital image. When audio is recorded, sound is picked up by a microphone and travels to the analog-to-digital converter (ADC) as electrical current.
The ADC takes several samples of the current and assigns them a sequence of binary digits (several 1s and 0s); Think of samples as the audio equivalent of pixels.
Just like more pixels per square inch means a sharper image, more samples per second means sharper sound. The number of samples taken per second is called the sample rate.
Standard sampling rate
There are standard sample rates that software and hardware companies must be compatible with in order for everything to work properly. If you are working on audio, you should be familiar with some of the standards. For example, 8 kHz is a standard sampling rate for recording the human voice. This is the minimum sample rate to understand speech; lower, and the listener will have difficulty determining the words.
When it comes to music, CD quality audio has a sample rate of 44.1 kHz. This means that the ADC takes 44,100 samples per second! It only goes up from there, because the next standard is 48 kHz; this sample rate is used more for movie soundtracks.
On the higher end of the spectrum, we have 96 kHz, which more than doubles the samples per second of 44.1 kHz and allows for clearer sound. However, there is controversy surrounding this sample rate, as people are generally not sure if 96kHz is needed.
Many experts believe that 96 kHz is just too much. Apple even offers 192 kHz audio!
What is bit depth?
Sample rate deals with audio clarity, while bit depth deals with the amount of noise in the audio. On returning, each sample is assigned a sequence of binary digits by the ADC. The number of binary digits per sample is called the bit depth.
The ADC assigns each sample the binary digits based on the amplitude of the audio (the strength of the current flowing from the microphone). This is how it reproduces the sound wave in digital form. The more bits per sample (the more output pins there are on the ACD), the more accurately the ADC can replicate the wave.
However, ADCs are only able to assign a finite number of voltages to each sample. So if a sample falls between two voltages, it is automatically rounded; this is called quantization noise.
The graphic above shows an example of a sound wave that was recorded via a 2-bit ADC. Even though the original wave (red) peaks at random levels, the quantized digital signal (blue) only arrives in 0.25 volt increments. Lower bit rates introduce digital noise to the audio because the lower the bit depth, the less accurately the wave is reproduced.
Standard bit depths
Just like with sample rate, there are different standard bit depths that you come across in the industry. 8-bit audio seems like the minimum bit depth you’ll see. With it you will hear a fair amount of noise, but the audio is still usable.
The next step is usually 16-bit audio, which is present with CD quality audio. Usually, you won’t hear any noise with 16-bit audio, and most people can record and edit it without much hassle. On top of that we have 24 bit audio. This bit depth is preferred by professional sound engineers. With 24-bit audio, you have zero noise and a better range of amplitudes to work with.
Finally, we have 32-bit audio, which is surrounded by controversy, much like the 96kHz sample rate. Many people believe this is not necessary. You can edit 16-bit and 24-bit audio very well, and 32-bit seems to be on top.
What is the optimal sample rate and bit depth?
So what are the optimal sample rates and bit depths for your needs?
Occasional listening
If you’re a casual listener, you won’t really need over 16-bit audio. Some services offer higher bit depths to make it look like clearer audio, but it doesn’t. You should also get away with a sample rate of 44.1kHz if you’re a casual listener.
Audiophiles and sound engineers
The conversation changes when it comes to audiophiles and sound engineers; they know what DACs are and use other equipment to get the most out of their music. 24-bit audio should be the best choice when it comes to noise and dynamic range. It can be softer without any audible noise and louder without any distortion.
As for the sample rate, the conversation gets a little muddy. Some people say they can’t tell the difference between 96kHz and 44.1kHz, while others say they can hear a difference.
Sample rate vs. bit depth: now you know
Technology can be tricky, and it gets worse with different terms being thrown out without any explanation. We come across sample rate and bit depth all the time when dealing with digital audio, and knowing more about these terms will help you better understand what you’re listening to.
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