100 mm

IntroductionAudible signaling devices by PfannenbergOur comprehensive range includes:• electronic multi-tone sounders• electronic multi-tone sirens and horns• programmable voice sounders(also in synchronised versions)• loudspeakers• combined signaling devices• buzzers and panel mounted buzzers• acoustic signaling devices for the Ex areaBasic principles of acousticsA source of sound causes the air to oscillate, resulting in alternating compression and relaxation of the air. Thispressure wave propagates itself in the form of a wave and causes the eardrum to oscillate, triggering the processof hearing.The sound pressure of oscillation is measured in microbars (μbar). The number of oscillations per second is calledthe frequency. Its unit of measurement is Hertz (Hz).Different types of sound• a harmonic oscillation produces a tone• a sound represents a mixture of tones• noise is the name given to a mixture of numerous tones, rapidly changing frequencies and rapidly changingsound volumes• a bang is produced by a sudden beginning of a mechanical oscillation of very short duration and great loudnessSoundpressurehigh tone:manylow tone:few oscillations per secondSoundpressureImpulse(hammer)SoundpressureMachine noisetimetimetimeSoundpressurequiet toneloud toneSoundpressureToneSoundpressureSoundtimetimetimeProperties of sound waves:• the number of vibrations per unit of time = frequency• range of the oscillation = amplitudeA large number of audio samples of different tones are available at www.pfannenberg.com/service.26