The Analog to Digital Conversion Process

Overview of Sound

We have established that sound is pressure variations in the air – which is continually variable.

This is a constant process and computers cannot comprehend this type of information.

Computers can only understand binary information. That is – strings of numbers – represented in 1 and 0s.

Analog to Digital conversion is the process of changing continually variable sound into a stream of ones and zeros (binary information). This process is known as Sampling.

Analog to digital conversion takes place during the recording process when sound is picked up by a microphone, is transported to the Audio Interface and is converted into digital audio which can be understood by your computer and accessed by your DAW.

 

Sampling

Binary information is based on the bit. A single bit is a 1 or a 0. Every number is collections of those ones and zeros.

The number of bits determines the maximum number of states, or the biggest number that you can represent.

A single bit can represent either states such as ‘on or off’, ‘heads or tails’ or a number from ’0 to 1’.

To represent larger numbers we collect bits into words (a collection of bits). In music production Midi data uses 7 bit words. Digital audio uses 16 bit words.

2 to the power of the word length – gives you the number or value. For example 4 bits (2 to the power 4) has 16 values. Adding one bit doubles the resolution, adding two quadruples it etc. This can increase quickly – 16 bit has 65,536 values.

 

Digital Audio Sound

These are the standards for digital audio sound:

CD – 16 bits

Studio – 24 bit

We record in the studio at a higher bit rate than what ends up of the finished CD recording. This means there is a wider dynamic range (resolution) when we are recording – and we can record at a quieter level – which decreases the possibility of distortion.

There are two really important parameters in digital audio. Word length which is related to amplitude and sampling rate which is related to frequency.

 

Set your DAW Bit Rate

Bit rate – 24 bits

Be aware its best not to alter this setting while you are recording a project which can create problems.

Sampling Rate refers to the multitude of measurements per second that take place during recording. And the sampling rate can measure over 40,000 times per second to accurately represent the continuously variable signals in the air as digital. The higher the sampling rate – the higher the frequency that can be represented as digital.

 

CD Sampling Rate

CD Sampling rate is 44,100 hertz

Frequency is half the sampling rate. For example if you use a sampling rate of 44,100 hertz for music CDs then the frequency will be 22,050 hertz. This is higher than the top end of the human hearing range which is 20,000 hertz. So the CD sampling rate of 44,100 hertz covers everything humans can hear. Another common sampling rate is 48,000 hertz which is used in video production and editing.

 

Set your DAW Sampling Rate

Sampling rate – 48,000 hertz

When recording watch out for sample rate mismatch as this can speed up or slow down the audio.

Bear in mind that a single sample can have a dramatic impact on your audio and the quality of your audio (clicks, pops etc.). So listen very carefully on playback.

 

In Conclusion

Our understanding of the Analog to Digital conversion process helps us to excel in the music production process. It gives up a clear view of how the analog sounds we hear and record are converted into a digital form that computers can comprehend. We know and identify the importance of bit rate and sampling rate and how they relate to amplitude and frequency. We now have knowledge of the optimal settings for bit rates and sampling rates that we can use to make high quality recordings with our DAWs.