Headphone

A small loudspeaker (earphone) with headband worn in or over the ear. People use headphones in environments where they do not want to disturb others, such as when on an airplane or at the library Headphones can be a great tool for controlling listening privacy. A headphone may be worn with one or both of the earpieces depending on whether it has a microphone. This type is called a headset. In addition, stereo headphones are used for listening to stereophonic sound with a distinct channel of noise fed to each earphone.

This article was most recently revised and updated by Hamza Khan

Sound Recording

–> The process of converting vibrations in air into sound and storing them for future use on a storage device or media for instance a phonograph disc. In sound reproduction process, the role played by the variations and fluctuations as recorded on the medium is to be reversed, that is, these fluctuations are responded for to produce sound waves. The three main physical media that have evolved in the process of sound recording and reproduction includes the mechanical media also known as phonographic disc, magnetic or audiotape media and the optical media or the digital compact disc . They include such recordings as audio or video that are commonly practiced as forms of mass media.

The Phonograph Disc

–> A monaural phonograph record includes a plastic disc with a crosswise spiral 90° V-shaped groove impressed on the product. While the record is rotating at 33 1/3 revolutions per minute, a very fine ‘needle,’ or stylus, traces into the groove and oscillates in the proper direction to the surface of the record and at right angle to the groove to depict the sound. The one is thus has to adjustably fit into the second-end to attach to a tiny magnet, which is vibrated back and forth through a small coil to generate an electrical voltage resembling that of the originally sought after sound wave. The up-down motion of the stylus characterizes the frequency of the sound produced and the loudness of the sound produced is characterized by the amplitude of the oscillation of the stylus.

As with depth of vision having two eyes, the same with stereophonic or recording two equipments using two microphones, playing in two separated loudspeakers. Stereophonic recording entails that the two are signal channels are provided as oscillation in a plane perpendicular to either one or the other face of the record groove. The single coil of the monaural pickup that had originally been pick up by a single coil to gives two signals perpendicular to the motion of the stylus to each groove wall, the inside being the left channel and the outside being the right channel. These two signals are then passed through an audio amplifier and to the loudspeaker as mentioned below.

The criteria for deciding whether a recording has adequate frequency control are that the change in frequency cannot be detected by ear. Unlike the pure organic phosphates and the organic phosphates with co-ordinated water, the organic phosphates with simple anions have absorbed less than about 0. Percentage change < 1 percent which is below the JND of frequency change over the major parts of the audible frequency spectrum. This can be done by using a heavy turntable and a precision motor to ensure that the speed of the record is correctly controlled to remove both wow, slow fluctuations in the speed of the recording and flutter, the rapid fluctuations in the speed of recording. A vibration that is produced when the turntable rotates is separated from the stylus providing no rumble. The stylus is conical that has an ellipse with its major axis lying across the groove. Compliance is normally measured by the stylus’s ability to conform to the groove and leave a linear trace on the medium; this is why the tip of the stylus is usually made of industrial diamond and has to be no larger than 25 micrometres across .

Among new interesting concepts associated with the theory of phonograph records in terms of Faraday’s law of magnetic induction we have the following. As mentioned in the above law, the electric potential which lies generated in the coil of the magnetic pickup is directly proportional to the field of the moving magnet in the pickup and inversely proportional to the time period of oscillation. However, what is required in the synchronizing system, is the constant amplitude of the sound wave across the spectrum, and this requires reducing the amplitude of the stylus’s motion at high frequencies and, conversely, increasing that motion at low frequencies more significantly. However, certain restrictions on the compliance of the accrual of such a scheme indicate that the stylus can not sufficiently accurately track an oscillation of large enough amplitude at a low limit frequency. Moreover, due to the nature of the serial reproduction of phonographic recordings the plastic material gives off high-frequency graininess of the stylus