Handbook for Sound Engineers

Test and Measurement 1625

46.3.6 Human Perception

Useful measurement systems can measure the impulse
response of a loudspeaker/room combination with great
detail. Information regarding speech intelligibility and
music clarity can be derived from the impulse response.
In nearly all cases, this involves postprocessing the
impulse response using one of several clarity measure
metrics.

46.3.6.1 Percentage Articulation Loss of Consonants-

(%Alcons)

For speech, one such metric is the percentage articula-

tion loss of consonants, or %Alcons. Though not in

widespread use today, a look at it can provide insight

into the requirements for good speech intelligibility. A

%Alcons measurement begins with an impulse

response, which is usually displayed as a log-squared

response or ETC. Since the calculation essentially

Figure 46-24. A short time window isolates the direct field at high frequencies at the expense of low-frequency resolution,
SIA-SMAART.

Figure 46-25. A long time window provides good low-frequency detail, SIA-SMAART.