In order to play back the recorded sound better, in 19 10, S. G. Brown separated the driving force from the diaphragm and invented the armature earphone. 19 10, Baldwin invented the balanced armature earphone. Armature earphone is a movable iron plate (armature) installed in the middle of U-shaped magnet. When current flows through the coil, the armature will be magnetized, and the magnets will repel each other and drive the diaphragm to move. This design cost is low, although the effect is not good, but it was also an epoch-making invention at that time. This technology is mostly used in telephone handsets and small headphones.
In recording technology, in 19 17, Winter and Tourasse designed a condenser microphone.
In the mid-1930s, according to the principle of condenser microphone, electrostatic speaker appeared. In the early 1950s, American C. V. Bocciarelli put forward the law of "constant charge". P. Walker independently developed the same theory in the same period and applied it to the design of the famous Quad electrostatic speaker.
The basic principle of electrostatic loudspeaker is Coulomb's law. Generally, plastic diaphragms and sensing materials such as aluminum are evaporated in a vacuum. The two diaphragms are placed face to face. When positive current and high voltage are applied to one of them, the other will induce a small current, and air can be pushed to make a sound through mutual attraction and repulsion. Because of the light weight of electrostatic monomer and small vibration dispersion, electrostatic speaker works in the middle and high frequency band, with light and meticulous sound quality and rich characteristics, and it is easy to get clear and transparent middle and high notes. However, its low efficiency, low sound pressure output, small dynamics and high cost are also its weaknesses. At the same time as Bell, different speaker types are proposed. As an amateur, Ernst W. Siemens (Siemens &; 1874,65438)1On October 20th, the founder of Halske Company applied for a patent for a prototype of an electric loudspeaker, in which a voice coil with a supporting system was made in a magnetic field to keep the vibration system moving axially. At that time, it was mainly used in the field of relays rather than speakers. 1877 14 February 14, Siemens applied for a patent for a loudspeaker, and pasted parchment on a moving voice coil as a sound radiator. Parchment can be made into an exponential cone, which is the first full-size loudspeaker in the phonograph era.
1898, Oliver lodge applied for the first patent of practical electric loudspeaker, which moved the voice coil into the magnetic gap between the inner and outer circular plates. Like many inventions, this great invention was too advanced at that time. According to the invention, the structure of 99% of modern moving-coil loudspeakers is determined in 20 14.
Twenty-five years later, in the 1920s, radio broadcasting appeared. C. W. Rice and E. W. Kellogg published an epoch-making paper "A New Type of Non-trumpet Unit", which introduced the direct loudspeaker in detail. The Radiola 104 loudspeaker designed based on this theory costs $250 and is very popular in the United States.
In the past 50 years, the basic principle of electric speakers has not changed, but the design details and components have been improved. Compared with the old products, the frequency response range and dynamic range have made great progress. The electric loudspeaker has become the mainstream of the market in 20 14 years because of its advantages of simple structure, excellent sound quality, low cost and dynamic.
Electric speakers are widely used, which can be divided into three types: paper basin type, horn type and dome type. Only the first two are introduced here.
1, paper basin speaker
Paper cone speaker is also called dynamic speaker.
It consists of three parts: ① vibration system, including cone-shaped paper basin, voice coil and centering bracket; (2) Magnetic circuit system, including permanent magnet, magnetic conducting plate and exciting stem; (3) Auxiliary system, including basin frame, wiring board, blank holder and dust cover, etc. When an audio current flows through the voice coil in the magnetic field, it will generate a magnetic field that varies with the audio current. This magnetic field interacts with the magnetic field of the permanent magnet to make the voice coil vibrate in the axial direction. Because of the simple structure, full bass, soft sound quality and wide frequency band, the efficiency is low.
2. Small speakers
The structure of loudspeaker is composed of vibration system (tweeter) and loudspeaker. The vibration system is similar to a paper basin speaker, except that its diaphragm is not a paper basin, but a dome-shaped diaphragm. The vibration of the diaphragm radiates sound waves into the air through the horn (after two reflections). High frequency, loud volume, often used for outdoor and square sound reinforcement. In the process of the formation of the above speaker technology, people began to understand that the ideal transducer should use a thin diaphragm that can pass current, and everyone began to conceive a belt speaker.
Schottky and Gerlach of Siemens Halske applied for the first patent of belt loudspeaker in June 1923. It installs a horizontal wave-shaped pure aluminum film between the two poles of the magnet, which can reduce the longitudinal hardness and resonance frequency.
193 1 year, Olson and Massa produced tape microphones.
Belt speakers are mainly used in middle and high frequency bands. Because of its flat frequency response curve, extremely high upper frequency limit and very good transient effect, it can easily form a linear sound source.
Although the history of human electroacoustic is so tortuous and complicated, there are indeed many excellent innovative electroacoustic speakers, and in fact, the design of these innovative speakers has tortured many of the best electroacoustic scientists in the last century. Horn (loudspeaker), commonly known as the Horn of Africa, is an indispensable equipment and sound system. Everyone in the trumpet listens to music and enjoys it. Because of entering the "acoustic energy", the quality and angle of the electrical energy of the only equipment play a decisive role in the sound and characteristics of the whole sound system.
Horn's sound system stands out in the car. In order to show a good tone and direction, some speakers and their layout are very important criteria. Speakers and effects: In the field of car audio, people have been pursuing such effects: they like to sit in front of the stage in the car because all the sounds are used on the windshield, hair and eyes, and they like the feeling of being in a concert. You can achieve the best reproduction of the sound of each instrument. This is what is commonly called professional Hi-Fi (high fidelity, high definition). The key of ideal high fidelity effect is to synchronize the amplification of sound source and signal in the same frequency band. Home stereo is not difficult. Because the high-frequency unit of household audio is in the same fixed frame, all music signals are amplified by the same amplifier, so it is easier to reduce the proportion uniformly and achieve a good sound quality balance. However, due to the limitation of different car audio installation positions, the subwoofer unit can only be installed in the luggage compartment, the bass unit can only be installed in front of the car, and the tweeter unit is usually installed near the A-pillar. This effect may only come from the contrast of high and low voices on the back of the same month, and the midrange part is weak. In addition, according to the requirements of different modules and power amplification, the general car audio can only use a variety of power amplifiers to drive the speakers (many low-frequency parts of the design need multiple power amplifiers to amplify), so it is difficult to achieve a satisfactory tone balance level. The number and installation arrangement of speakers is one of the key factors to meet these challenges. Number of speakers
The speaker volume can determine the fineness of the specified sound direction, and the small one is rougher. More advanced than ordinary vehicles, car horns. The installation position of the horn is often affected by the sound effect of the car stereo, and the same horn of two companies will have different effects in different installation positions. The installation position of middle and high-grade car horns must be determined through various tests. With the correct installation experience and skills, the number of speakers can cope with the installation positions of speakers with different bandwidths, maintain a good direction, and adjust the power amplifier with compatible technologies, and finally achieve good results. From a professional point of view, the installation layout has a direct impact on the Hi-Fi effect and an excellent balance on the hi-fi sound quality. The audio-visual effects of the front sound field effect (the sound effect is pre-perceived), the sound field position (the influence of different sound sources in other places and the positioning accuracy), the sense of space (the bass response of the spatial acoustic effect), the playback effect (the restoration of high-fidelity sound effect) and (the sound, pitch and image quality results) are respectively. Good underwater acoustic positioning (segmentation) largely depends on the setting of tweeters around the cab and midrange units in front of the cab. Because the human auditory system is mainly in the audio part where sound waves reach the left and right ear rate sound sources successively. The tweeter and loudspeaker installed near the door can form a consistent and coordinated sound source only by installing the intermediate points that are frequently matched. Considering that the left and right sound angles of the audience also depend on the position of the sound horn, it is repeatedly adjusted accurately to make the car sound achieve good sound field positioning. Therefore, the layout of car speakers is very important for car acoustics. At the 2nd International Expo of 20 14, scientists from Fudan University said that they had successfully invented the "forced stop artifact" of square dance noise-active directional speakers.
The sound emitted by ordinary speakers spreads in all directions. In order to achieve orientation, the diameter of the speaker must be very large. Different from the principle of traditional speakers, active directional speakers first load low-frequency sound signals on high-frequency signals with strong directivity, and then amplify them and emit them into the air. Then, the air will quickly filter the high-frequency signals, and the audible sound signals above will naturally be filtered out, realizing directional propagation like laser.
Active directional speakers can control sound waves in a specific area, where the sound waves are strong, and outside this area, the sound waves will be weak or even absent. If the square dancers use this horn to play music, the' embarrassment' of disturbing the people will be solved. "Ma Jianmin said. In addition to being the "forced stop artifact" of square dance noise, active directional speakers can also be used in advertising exhibitions, waiting halls, bus stops and other scenes to realize directional sound playback for specific people.
20 14 there is no finished product in the domestic market, and the "artifact" is expected to be officially unveiled at the end of this year. Optimists believe that if it can be listed in large quantities, it may solve the problem of noise disturbing people in square dance. The speakers in win7 system are always automatically disabled.
1. Right-click the computer icon and select Properties.
2. Switch to the "Hardware" tab, select the sound card device in the device manager, right-click to delete the device, find the menu bar to operate, scan for changes, and the system will pop up a prompt that the sound card is being installed, and it will be normal after about 1 minute;
3. In addition, it is also possible that the driver is disabled. I suggest you go to the device manager to find and right-click the audio device, select uninstall, including deleting the driver, then scan the hardware and let the system install the driver by itself.