100 mm

IntroductionTypes of sound generationSound capsule – electromagnetic sound generationIn the sound capsule, anchors connected to the membrane arepre-magnetised by a permanent magnet. When a voltage isapplied, the membrane is stimulated to oscillate, generating soundwaves that are perceived as an audible tone. Despite its relativelysimple and compact structure, the sound capsule has a relativelyhigh efficiency level. For that reason this technology is often usedin appliances with small dimensions.Loudspeaker – electro-dynamic sound generationThe electro-dynamic loudspeaker consists of a membraneconnected to a central oscillating coil. This coil is located withinthe magnetic fi eld of a permanent magnet. If the voltage of thesignal to be transmitted is applied to this coil, an alternatingelectromagnetic fi eld is generated that causes the membraneto move and, hence, to generate sound pressure.Various membranes (smaller or larger, softer or harder) anddifferent coils and permanent magnets are used,depending on the frequency range. Electrodynamic loudspeakersare ideally suited for generating high sound pressure.Horn loudspeaker – electro-dynamic sound generationThe membrane in a horn loudspeaker acts on a very small space –the pressure chamber. The velocity of the air particles is increasedin this pressure chamber due to its small cross-sectional size. Thisprinciple increases effi ciency considerably in comparison to otherdesigns. Due to the high sound pressure, which can be attainedand the high frequency range that can be transmitted, horn loudspeakersare ideal for the transmission of sound in large areas.Horn loudspeakers are usually insensitive to weather and arevery robust.Piezo-electric effectAt the heart of a piezo loudspeaker is a crystal. When a voltageis applied to this crystal, it deforms as a result and is thus set inmotion. Piezo loudspeakers essentially transmit only higherfrequency ranges and are not suitable for penetrating throughobstructions such as walls. The advantage of these systems liesin their high impedance and, therefore, low power consumption.28