Ecler CKL Series, Руководство пользователя

Страница: 12 / 48

12
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:
6
10 · 20
log 20
−
=
ef
p
SPL (dB SPL)
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
SOUND PRESSURE
LEVEL (dB SPL)
SUBJECTIVE LEVEL
SENSATION
Jet take-off 120
Very high
Construction works 110
Pneumatic drill 100
Heavy truck (at 15m) 90
High
City street 80
Inside car 70
Normal conversation 60
Moderate Office 50
Living room 40
Bed room (al night) 30
Low
Recording studio 20
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.
i
abs
E
E
= α
Values of
α
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)