Music Technology 101: Sampling Rate and Bit Depth Explained

In this short video I will explain two widely used terms in music technology: sampling rate and bit depth. We'll also take a look at analog to digital conversion along the way.

What is an analog to digital converter? (ADC)

This is a small electronic unit inside your sound card which is responsible for converting the analog voltage measured by your microphone or other inputs into a series of binary numbers your machine can store and "understand". All data in your computer is in binary format, made out of 1s and 0s.

What is Sampling Rate?

Sampling rate determines how many points of a signal you acquire per unit time. It is usually measured in hertz, also abbreviated Hz, where 1 Hz = 1 point per second. Some other units you'll run into are:
1 kilohertz = 1 kHz = 1000 Hz
1 megahertz = 1 MHz = 1,000,000 Hz
1 gigahertz = 1 GHz = 1,000,000,000 Hz
1 terrahertz = 1 THz = 1,000,000,000,000 Hz
Of course, in audio only Hz and kHz are used, since those are the frequencies the human ear can hear. Higher frequencies are not encountered, although other non-audio digital electronics do use them.
For example, a sampling rate of 100 Hz means your ADC takes 100 points per second. Most audio cards operate at much higher sampling rates: 48 kHz, 96 kHz or even 192 kHz. This is related to a mathematical theorem called Nyquist's Theorem: the sampling rate of an ideal ADC should be at least twice the maximum frequency of your signal. Since our ears cannot hear above around 20-22 kHz - if they're really good! - sampling rates usually have to be at least around 40-44 kHz. Note that I said ideal ADC. Because of real-world non-ideal conditions, sampling rates are usually taken to be higher than twice the maximal frequency. This allows ADCs to deal better with their non-idealness.

Here's a pretty cool online hearing test, albeit not a very scientifically rigorous one, to help you determine the maximal frequency you can hear:

http://www.noiseaddicts.com/2009/03/c...

Sampling rate on Wikipedia:
http://en.wikipedia.org/wiki/Sampling...

What is Bit Depth?

Sampling rate tells you HOW MANY points you acquire per second. Bit depth tells you HOW DETAILED is each point. In computer jargon, this means how many bits of information you use to represent each point using binary numbers. Think of bit depth as putting a vertical ruler on your sound wave and rounding up each value to the nearest point on the ruler. The higher the bit-depth, the finer (smaller) the distance between the points. You can read about bit depth in more depth (pun intended) on Wikipedia:

http://en.wikipedia.org/wiki/Audio_bi...

Related Videos

I have many other music and audio video lessons on Youtube which I invite you to check out (although it IS skewed in favor of playing the piano). Some examples:

The physics of wind instruments:
   • Видео  
Fun with delays:
   • Piano Lesson: Play twice as fast - fu...  
Learn to read sheet music for beginners:
   • Reading Sheet Music for Beginners (1/4)  
Jazz piano harmony and voicing:
   • Jazz Piano Harmony: Chord Voicings, t...  
Learn to play fast piano runs:
   • Learn to Play: Fast Piano Runs (Fills)  

Other People's Videos

There are quite a few good online video lessons discussing sampling rates, bit depth and analog to digital conversion. These are a bit more advanced than what shown here, but still worth checking out if you have the technical aspirations:

Sensing - introduction to robotics:
   • Introduction to Robotics Course -- Le...  
More about ADCs:
   • Analog to Digital Converters (ADC) Pa...  
In an depth lesson from IIT in India (it's in English):
   • Lecture 18 - ADC Terminology, Offset ...