Digital Audio Waveform Tutorial for Beginners in Music Production

4.) Peak Amplitude – This is the maximum peak in the entire waveform (from beginning to end). For example in the above screenshot, there are two values -3.98 dBFS for left and -5.9 dBFS for right because the waveform is stereo (two-channels). Since the peak amplitude is less than 0dBFS there will be no clipped signal as confirmed by the statistics. Peak amplitude is very useful in recording and mixing digital audio. For example, an important recording clipping prevention technique in recording/tracking is to never exceed -6dBFS peak from start to end. This will ensure you have a lot of headroom in your digital audio which will also prevent distortion/clipping at the same time. In some recording sessions, this may increase to -3dBFS as long as no signal will peak at 0dBFS or more. During audio mixing, all tracks peak amplitude as well as the mix down should never exceed -3 dBFS in order to have correct audio mixing levels and headroom in preparation for mastering.

5.) Minimum RMS power – this is the lowest “RMS” volume detected on the waveform. Take note that this is not “peak” measurement but rather “RMS”.

6.) Maximum RMS power – the loudest RMS volume detected on the waveform.

7.) Average RMS power – this is the average perceived loudness of the entire waveform. This is a very useful measurement used by mastering engineers to determine the resulting loudness after mastering. For example, rock CD albums released today usually have an average RMS power of -12dBFS to -10dBFS (which is loud). -15dBFS to -13dBFS is considered not too smooth or too loud. The loudest CD that participates in the loudness war could have average RMS power of -7dBFS.

8.) Actual Bit depth – this is the bit resolution used in the digital audio. If it shows 32-bit, it is exactly a 32-bit float system: that utilizes a 24-bit accuracy with additional 8-bit float. The maximum dynamic range (maximum possible difference between loudest and softest volume) of the digital audio waveform is related by the bit depth and can be approximated by: 6.0206 x bit depth + 1.761. So for an audio with 24-bit resolution, the dynamic range is: Dynamic range = 6.0206 x 24 + 1.761 ~146dBFS

In most applications: Maximum RMS power – Minimum RMS power < Maximum Dynamic range. You increase the dynamic range and get more headroom by using a higher bit depth during the recording/tracking session. Aside from the waveform properties in statistics, you can also view the waveform properties by going to View – Waveform properties and click the File info tab in Adobe Audition (in other recording software you can find similar functionality to this one). It is shown below:

waveform properties like sample rate

waveform properties like sample rate

The following are the waveform properties shown:

9.) Sample rate – in the above screenshot, the sample rate is 44100Hz. When recording/tracking, the most recommended sample rate should be greater than 44100Hz. Common values are 48 KHz, 88.1 KHz, 96 KHz and 192 KHz.

10.) Uncompressed size – this is the file size of the WAV file.

The last important property is the frequency characteristics of the digital audio waveform which you can see by doing a frequency spectrum analysis plot of the waveform. This will convert the time domain function (amplitude vs. time) to (amplitude vs. frequency). See the equivalent waveform in frequency domain:

frequency domain plot

frequency domain plot

Thus it shows that below 40Hz, there is less energy as compared to 50Hz and 500Hz (where most energy is concentrated). There is also less mid frequency content from 1000Hz to 3000Hz and even lesser high-frequency energy. These frequency characteristics will be used by engineers to confirm the frequency content of the signal in relation to any EQ implementation.

Content last updated on August 8, 2012