Sound

Some useful terms

• decibel (dB)

  • This is a unitless measure of the difference between two different waveforms. Generally, the comparison waveform is near silence, so the measured one is then relative to this baseline. It is logarithmic, meaning that something 10x twice as powerful is +10dB. +20dB would be 100x more powerful.  Power and perceived loudness are different things, as +10dB will sound twice as loud (but still be 10x more powerful)

• Volume

  • Volume is the adjustment made on a given playback device. It increases the power sent to the speakers, etc., to amplify the sound

• Loudness

  • This is defined by the characteristics of the audio, and the amplitude of waveforms.  Humans hear logarithmically and part of what makes something feel loud is how long the waveform sustains a given 

• dB RMS

  • Decibel root-mean-squared. A method of measuring the average amplitude but if there are any long periods of soft or very quiet periods, this can significantly skew the average amplitude.  This is not as useful as LUFS and LKFS

• LKFS/LUFS

  • Loudness units k-weighted relative to full scale (LKFS) or Loudness units relative to full scale (LUFS). They are the same thing (just named differently by different countries' standards organisations). These may be a mouthful but are fairly easy to understand and use. Unlike dB RMS, it removes any portions below -70dB so it only calculates portions that are perceptible by the average human hearing. It does this over the entire length of the audio being examined (e.g. a TV programme, radio broadcast or YouTube video).

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