Attenuation versus frequency characteristic. The attenuation versus frequency characteristic of a
circuit is the amount of loss through the circuit as a function of frequency. The function is usually
shown with the amplitude in decibles relative to a certain reference level on the vertical scale, and the
frequency on the horizontal scale. Figure 5-4 illustrates the attenuation versus frequency characteristics
curve for an audio low pass filter. This low pass filter was designed for use on an intelligibility
enhancer for a voice-communications circuit.
a. Various devices are used for precise adjustments of the characteristics of attenuation versus
b. For instance, in high-fidelity recording equipment the equalizer is often used instead of the
bass and treble controls to help obtain the desired audio response.
Figure 5-4. Attenuation. Attenuation versus frequency characteristics of a lowpass filter that might be
used for communication purposes
Learning Event 2:
DESCRIBE AND IDENTIFY THE COMPONENTS AND FUNCTIONS OF A TYPICAL AUDIO
Speakers. Speakers transform energy from one form to another; i.e., electrical to mechanical
energy. The speaker will convert the audio signal sent to it from the amplifier and change it into a
instantaneous pumping motion. This motion (fig 5-5) is strong enough to transport air in vibrating
patterns of waves that the ear hears as sound.
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