How to make canned sound more tasty? – Talking about compression and audio encoding
Last time I talked about [How to make canned goods sound more delicious? ——A brief talk about audio compression and encoding (Part 1) ], the main job of the audio compression algorithm is to compress the part of the frequency beyond the range of the human ear and the part that is “inefficient” for the human perception For these contents, What we need to know: auditory masking effects
auditory masking effect
In 1894, the American physicist Alfred M. Mayer reported that a tone could be masked by another tone of lower frequency. In 1959, Richard Ehmer described a complete set of auditory curves for this phenomenon. Between 1967 and 1974, Eberhard Zwicker worked in the field of tuning and masking of key frequency bands. Auditory masking effects can be divided into “simultaneous masking” and “temporary masking”.
“Simultaneous masking” refers to the phenomenon that two sounds of different frequencies are played at the same time. Due to the characteristics of human perception of sound, a weaker signal is masked by another signal. In summary, pure tone masking has the following characteristics: bass is easy to mask from treble, and treble is more difficult to mask from bass; pure tones with similar frequencies are easy to mask each other; when the sound pressure level of the masking sound increases, the masking threshold will increase and the masked sound will increase. The frequency range will expand. Here is a schematic diagram to describe this phenomenon
as shown in the figures, the masking effect masks signals at approximately 0.7 kHz, 1.6 kHz, and 2.3 kHz, where the SPL of the 0.7 kHz signal is below the threshold of listening and cannot be heard without masking.
On this basis, three important concepts SMR, SNR and MNR are introduced. mutual relationship
