What is a waveform, like the ones on SoundCloud a graph of? What labels would you put on the axes?

For example, this is a waveform of Morse code. I can tell that the X-axis is time, but what is the Y-axis?

enter image description here

2 Answers 2


X-axis is the time axis, Y axis represents the sample value at that point in time. The X axis always represents an increasing positive value (Left to Right) however the Y (sample value) axis can be negative or positive. In the example given (morse code = LHR) it is likely a sine-wave that forms the morse signal, therefore the positive peak will be a similar value to the negative peak. You can see this as the waveform is roughly symmetrical around the center.

As for scale, you will often find the term dBFS (Decibels relative to Full Scale) as the Y-Axis unit. The peak value will be 0 dBFS and the null value will be -∞ dBFS. This is more likely to be seen on a scale where you only see the positive excursion of the sample value.

  • Thank you Mark! So, for audio signals such as this one, would "amplitude" be a good label for the Y-axis? Commented Jun 29, 2019 at 9:44
  • Yes, it would be fine to use 'amplitude' for this.
    – Mark
    Commented Jun 29, 2019 at 10:41
  • 1
    VK3ZQ here. QSL?
    – Mark
    Commented Jun 29, 2019 at 11:27
  • I should've known this question would connect me with a ham. I'm not licensed yet :) Commented Jun 29, 2019 at 14:45
  • 2
    haha we're evvvvvrywhere ;-) Hope you enjoy the hobby mate. See you on ft8 when you get your license!
    – Mark
    Commented Jun 30, 2019 at 9:37

The Y-axis represents amplitude, and the X-axis represents time.

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