Sound Pressure Level (SPL) of Voice and Speech and How to Measure It

What is it about?

SPL of voice and speech is generally used to measure "voice intensity". This measurement is often considered a trivial matter, but the measured levels are often reported incorrectly or incompletely, making them difficult to compare among various studies. This article aims at explaining the fundamental principles behind these measurements and providing guidelines to improve their accuracy and reproducibility. Method Basic information is put together from standards, technical, voice and speech literature, and practical experience of the authors and is explained for nontechnical readers. Results Variation of SPL with distance, sound level meters and their accuracy, frequency and time weightings, and background noise topics are reviewed. Several calibration procedures for SPL measurements are described for stand-mounted and head-mounted microphones. Conclusions SPL of voice and speech should be reported together with the mouth-to-microphone distance so that the levels can be related to vocal power. Sound level measurement settings (i.e., frequency weighting and time weighting/averaging) should always be specified. Classified sound level meters should be used to assure measurement accuracy. Head-mounted microphones placed at the proximity of the mouth improve signal-to-noise ratio and can be taken advantage of for voice SPL measurements when calibrated. Background noise levels should be reported besides the sound levels of voice and speech.

Featured Image

Why is it important?

There are different ways to measure SPL of voice speech which can give different results when measuring the same phenomena. There are different software packages and different equipments available for measuring SPL but they are often being used without clear understanding which makes the results problematic to compare and reproduce. This paper attempts to fill in the gap, explains the basic principles behind SPL measurement and provides recommendations in order to improve reproducibility of the results from different labs and from different equipment.

Perspectives