Appendix - Brief Explanation Of Acoustic Concepts; Definition Of Acoustic Parameters; Sound Pressure Level (Spl); Acoustic Absorption - Ecler CKL Série Manuel Utilisateur

8. APPENDIX – BRIEF EXPLANATION OF ACOUSTIC CONCEPTS
The following paragraphs give brief explanations of frequently used concepts in acoustics, which will
help you understand the problematic involved in designing high-quality PA systems.

8.1. Definition of acoustic parameters

8.1.1. Sound Pressure Level (SPL)

Defined as:
p

ef
SPL 20 log

6
20 · 10
The numerator corresponds to the effective sound pressure.
The denominator corresponds to the hearing threshold, i.e. the minimum sound pressure which causes
hearing sensation in the human auditory system.
Following table shows the sound pressure levels of several typical sound sources, together with their
subjective level sensation.
SOUND SOURCE
Jet take-off
Construction works
Pneumatic drill
Heavy truck (at 15m)
City street
Inside car
Normal conversation
Office
Living room
Bed room (al night)
Recording studio
Typical sound pressure levels (dB SPL)

8.1.2. Acoustic absorption

The acoustic absorption coefficient is defined as the ratio between absorbed acoustic energy by a
certain material and incident acoustic energy.
E
 
abs
E
i
Values of  range between 0 (no absorption) and 1 (maximum absorption). The absorption
characteristics of construction materials used for acoustic treatment of rooms, determine, amongst other
factors, the resulting reverberation time. (see paragraph 8.2.2)
12
(dB SPL)
SOUND PRESSURE
LEVEL (dB SPL)
120
110
100
90
80
70
60
50
40
30
20
SUBJECTIVE LEVEL
SENSATION
Very high
High
Moderate
Low