“loudspeaker”的概念、定义、翻译、参考文献-科学参考

loudspeaker

Physics

A transducer for converting an electrical signal into an acoustic signal. Usually it is important to preserve as many characteristics of the electrical waveform as possible. The device must be capable of reproducing frequencies in the range 150–8000 hertz for speech and 20–20 000 Hz for music.

The most common loudspeaker consists of a moving-coil device. In this a cone-shaped diaphragm is attached to a coil of wire and made to vibrate in accordance with the electrical signal by the interaction between the current passing through the coil and a steady magnetic field from a permanent magnet surrounding it.

Electronics and Electrical Engineering

An electroacoustic device that converts electrical energy into sound energy. It is the final unit of any sound reproducer or of the acoustic circuit of any broadcast receiver. Its action is the reverse of that of the microphone but it is designed to handle far greater power, enabling the sound output to be audible over a large area.
Most types of loudspeaker use a coil and diaphragm arrangement in which a small coil is fixed at the centre of a diaphragm that is free to move in an annular gap. A strong magnetic field, produced by either a permanent magnet or an electromagnet, is applied across the gap. The audio signal is input to the coil as alternating current, causing it to move in the magnetic field as a result of electromagnetic induction. The diaphragm is thus caused to vibrate at the same frequency as the alternating current and sound waves are produced by it. Any loudspeaker using this arrangement can be described as a magnetic loudspeaker.
For high efficiency (up to 50% of energy conversion) a horn loudspeaker is used. This type of speaker uses a small diaphragm at the mouth of a large exponential horn, and has marked directional properties. The horn speaker is impractical for most indoor uses as it is very large. A more convenient size is achieved using a large conical or ellipsoidal diaphragm, usually made of stiff paper, with the coil at its apex. The cone is supported round its edge by a metal frame, and the coil is maintained in position at the centre of the gap by thin flexible supports known as a spider. A large baffle, usually the cabinet housing the speaker, is used with this cone loudspeaker to prevent the direct passage of sound from front to back and thus improve the low-frequency response.
A simple cone loudspeaker has a uniform power output over a moderate range of frequencies but the output falls at the high- and low-frequency ends of the audible spectrum. For good reproduction at low frequencies a large cone is required in order to give a larger radiation resistance at these frequencies. At high frequencies the mass of the vibrating system sets an upper limit for good reproduction and a small cone is required to optimize the response at these frequencies. Two speakers are sometimes used together in order to overcome these requirements: a large cone for the low notes and a small one for the high notes. The large cone is designed to have a very low resonant frequency to improve its output and the strong resonant peaks, which would cause a boomy sound, are eliminated by using considerable damping (see damped). A frequency-selective network is required with this type of speaker in order to divide the spectrum between the two sound radiators.
Some speakers use an arrangement of multiple coils and cones designed to reduce the effective mass of the speaker at high frequencies. A well-designed speaker gives a uniform response between about 80 hertz and 10 000 hertz but its conversion efficiency is low. Cone loudspeakers are essentially omnidirectional but the use of a suitable cabinet can introduce directional properties if required.
Other methods of producing the sound vibrations are sometimes used. The crystal loudspeaker utilizes a piezoelectric crystal as the vibrating part. Magnetostriction is used in the magnetostriction loudspeaker and the vibrations of a magnetic armature produce the sound of a magnetic-armature loudspeaker. The action of electrostatic fields produces the mechanical movement in an electrostatic loudspeaker. Acoustic standing waves can be reduced by placing a loudspeaker in a special housing containing air chambers. Such an arrangement is termed a labyrinth loudspeaker.
A loudspeaker microphone is a dynamic loudspeaker that may also be used as a microphone. This arrangement is often used in an intercommunication (intercom) system enabling a single unit to be used for both speaking and listening. A manually operated switch connects the device to the appropriate circuit for the desired function. The most convenient arrangement is a push-button that returns automatically to the loudspeaker condition when pressure is removed from it.

单词	loudspeaker
释义	loudspeaker Physics A transducer for converting an electrical signal into an acoustic signal. Usually it is important to preserve as many characteristics of the electrical waveform as possible. The device must be capable of reproducing frequencies in the range 150–8000 hertz for speech and 20–20 000 Hz for music. The most common loudspeaker consists of a moving-coil device. In this a cone-shaped diaphragm is attached to a coil of wire and made to vibrate in accordance with the electrical signal by the interaction between the current passing through the coil and a steady magnetic field from a permanent magnet surrounding it. Electronics and Electrical Engineering An electroacoustic device that converts electrical energy into sound energy. It is the final unit of any sound reproducer or of the acoustic circuit of any broadcast receiver. Its action is the reverse of that of the microphone but it is designed to handle far greater power, enabling the sound output to be audible over a large area. Most types of loudspeaker use a coil and diaphragm arrangement in which a small coil is fixed at the centre of a diaphragm that is free to move in an annular gap. A strong magnetic field, produced by either a permanent magnet or an electromagnet, is applied across the gap. The audio signal is input to the coil as alternating current, causing it to move in the magnetic field as a result of electromagnetic induction. The diaphragm is thus caused to vibrate at the same frequency as the alternating current and sound waves are produced by it. Any loudspeaker using this arrangement can be described as a magnetic loudspeaker. For high efficiency (up to 50% of energy conversion) a horn loudspeaker is used. This type of speaker uses a small diaphragm at the mouth of a large exponential horn, and has marked directional properties. The horn speaker is impractical for most indoor uses as it is very large. A more convenient size is achieved using a large conical or ellipsoidal diaphragm, usually made of stiff paper, with the coil at its apex. The cone is supported round its edge by a metal frame, and the coil is maintained in position at the centre of the gap by thin flexible supports known as a spider. A large baffle, usually the cabinet housing the speaker, is used with this cone loudspeaker to prevent the direct passage of sound from front to back and thus improve the low-frequency response. A simple cone loudspeaker has a uniform power output over a moderate range of frequencies but the output falls at the high- and low-frequency ends of the audible spectrum. For good reproduction at low frequencies a large cone is required in order to give a larger radiation resistance at these frequencies. At high frequencies the mass of the vibrating system sets an upper limit for good reproduction and a small cone is required to optimize the response at these frequencies. Two speakers are sometimes used together in order to overcome these requirements: a large cone for the low notes and a small one for the high notes. The large cone is designed to have a very low resonant frequency to improve its output and the strong resonant peaks, which would cause a boomy sound, are eliminated by using considerable damping (see damped). A frequency-selective network is required with this type of speaker in order to divide the spectrum between the two sound radiators. Some speakers use an arrangement of multiple coils and cones designed to reduce the effective mass of the speaker at high frequencies. A well-designed speaker gives a uniform response between about 80 hertz and 10 000 hertz but its conversion efficiency is low. Cone loudspeakers are essentially omnidirectional but the use of a suitable cabinet can introduce directional properties if required. Other methods of producing the sound vibrations are sometimes used. The crystal loudspeaker utilizes a piezoelectric crystal as the vibrating part. Magnetostriction is used in the magnetostriction loudspeaker and the vibrations of a magnetic armature produce the sound of a magnetic-armature loudspeaker. The action of electrostatic fields produces the mechanical movement in an electrostatic loudspeaker. Acoustic standing waves can be reduced by placing a loudspeaker in a special housing containing air chambers. Such an arrangement is termed a labyrinth loudspeaker. A loudspeaker microphone is a dynamic loudspeaker that may also be used as a microphone. This arrangement is often used in an intercommunication (intercom) system enabling a single unit to be used for both speaking and listening. A manually operated switch connects the device to the appropriate circuit for the desired function. The most convenient arrangement is a push-button that returns automatically to the loudspeaker condition when pressure is removed from it.
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