You've probably come across the number 44100 in podcasting and audio production circles. This number is a sample rate. Sample rates are measured in ‘hertz' or ‘Hz', which means cycles per second.
Each sample in your audio is displayed as a dot, which is visible if you zoom right in on a waveform.
The higher the sample rate number, the more times the audio has been ‘sampled'. This determines audio quality and also file size.
If you think of your audio file as a photograph, the sample rate is essentially just like the amount of pixels that make up an image.
Take a look at each screenshot, which shows the amount of time the audio was sampled within 0.00050th of a second. 8000Hz was only sampled 5 times in that time period. 44100Hz was 23 times. 48000Hz was 25 times, whilst 96000Hz was way up at 50 times.
You'll have the option to select a Sample Rate prior to hitting record in your DAW (editing software) or digital recorder.
For example, in Audacity, if you look down in the bottom left hand corner you'll see the heading Project Rate (Hz) and a drop-down menu underneath it. By default, the number will be set at 44100, and I'd recommend just keeping it set at that too.
The sample rate of 44100Hz is standard for music and CDs and is the ideal rate to record all your podcast audio at.
Sound designers in game, film, and television will mainly work in 48000Hz, though some work as high as 96000Hz.
In Audacity, the lowest sample rate you can record at is 8000Hz (way too low), and the highest is 384000Hz (way too high).
What About Bit Depth?
Each audio sample – those little dots in your waveform – has a ‘bit depth', which determines the quality of the sound.
You will usually be asked to select a bit depth prior to recording a piece of audio. The most common bit depths are 16, 24, and 32.
The higher the number, the higher the quality, and the more the recording is able to accurately capture a noise with substantial difference in volume from its quietest parts to its loudest parts.
For this reason bit depth is much more important for musicians than it is to podcasters.
With spoken word podcast content there is no need to record any higher than 16 bit. Using 24 or 32 will only increase the size of your source material WAV files, and any improvement in quality will be inaudible to all but the most trained ears.
What About Bit Rates?
Another load of numbers you might come across are bit rates, you'll see these as 96kbps, 128kbps etc.
These aren't directly relevant to sample rates and bit depth, so don't worry. A bit rate is something you'll be asked to select when you mix your audio down to MP3 form. If you'd like to learn more about this, check out What Bitrate Should I Use For a Podcast?
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