∎ the… sound barrier, sound barrier Name for the cause of an aircraft's difficulties in accelerating to a speed faster than that of sound. the action or process of measuring the depth of the sea or other body of water. Thus, wherever sound is produ… Sounding, sound (April 17, 2003).Īcoustics, The area of physics known as acoustics is devoted to the study of the production, transmission, and reception of sound. "Parabola." MathWorld (Wolfram Research). (The bulbs of car headlights are placed at the foci of parabolic reflectors.) █ FURTHER READING: ELECTRONIC: All light emanating from a point source placed at the focus of a parabolic reflector will exit the reflector in the direction of the parabola's axis. Parabolic reflectors are also used to create light beams from point sources. On one hand, the shotgun design does not focus sound on the mike, and so is not as sensitive as the parabolic design on the other, the shotgun mike is less cumbersome and less open to off-axis sounds. In a parabolic microphone system, the microphone is placed at this point sound waves entering the dish parallel to the axis are focused on the microphone and, thus, amplified.Īnother type of directional microphone, the shotgun mike, attains directionality by embedding the microphone in a long, narrow, open-ended tube only sound approaching the mike along the axis of the tube can reach the mike.
All rays that enter a parabola parallel to its axis and are reflected from the curve (like light rays from a mirror) pass through a single point inside the parabola, the focus. (Mathematically, the two arms of the curve go on forever in building a parabolic reflector, the arms are cut short.) The "axis" of the parabola is a straight line that passes through it like a vertical line drawn through the center of a V. A parabola is an open curve resembling a V with a rounded point. This makes the parabolic microphone useful for recording localized sources of relatively faint sounds, such as conversations or bird calls, at a distance.Ī paraboloid reflector is used because of the unique geometrical properties of the parabola. Thus, the parabolic microphone is highly directional, that is, more sensitive to sound sources at which it is directly pointed than to other sources. Sound waves passing straight into the parabolic reflector are focused by it on the microphone sounds entering the reflector dish from other angles impinge directly on the microphone, but are not focused on it by the reflector. A parabolic microphone is an ordinary microphone mounted inside a sound-reflecting dish having a parabolic cross section.
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