A better way of measuring dynamic range?
Reply #1 – 2007-02-26 00:24:38
Interesting idea. It might be possible to come up with words to name the measures. Typically in classical music (and much other sheet music, especially piano music) the longer-term dynamics consist of the range including pianissimo, piano, mezzo-piano, mezzo-forte, forte and fortissimo. Crescendo and diminuendo would perhaps tend to be included as medium term dynamic variations (a gradual change over a few seconds). Sforzando would typically be instantaneous, punchy dynamics (and "transients"). I guess one might also consider changes of tempo and note duration to be part of "dynamics" available for artistic effect as defined by musicians, rather than the definition of dynamics as a purely loudness-based phenomenon that we tend to use.. In the regard to relating these measures to named characteristic, I have another thought: It's reasonably common to refer to the "punch" of a recording. While this is closest to your short-term measure, your reading is the difference between the 10th and 90th percentile. In the case where a song consists of, for example, a quiet intro with light orchestration followed by a much louder ending (I'm thinking of Aretha Franklin's dynamic version of Tracks Of My Tears), I would presume that the 10th percentile would surely come from the very soft first half of the song, while the 90th percentile would come from the lound last part of the song, so I wouldn't be happy to describe your 0.1 second measure as "punch". If I were interested in the degree of "transient punch" or "smoothness" in the rhythmic nature of the track, I'd be looking at a different measure to the short-term measure you chose. It might take a short instantaneous measure of loudness (over perhaps 25 to 50ms) and compare the peak and trough or peak and average, or perhaps various percentiles measured over averaging times of a few seconds throughout the song. One could report an instantaneous "punch" value that may vary throughout the song (and could even be displayed in an audio player, just as variable bitrate or a rolling spectrogram can be). Or that perceived loudness ratio (in dB), known as "transient punch" could be averaged or ranked in a cumulative distribution over the whole song to give an overall representative figure for "transient punch". Other words I can think of for long-term dynamic variations would include "light-and-shade" (or perhaps "contrast", keeping up the visual metaphor), and this could apply to 10s averaging time. A seafaring metaphor, such as "swell" might be adequate to describe the medium term (1s averaging) dynamic variation."