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CMRR is a measure of a system's ability to ignore such interference and especially hum at its input. It is generally only significant with long lines on an input, or when some kinds of ground loop problems exist. Unbalanced inputs do not have common mode resistance; induced noise on their inputs appears directly as noise or hum.
Sound quality is typically an assessment of the accuracy, fidelity, or intelligibility of audio output from an electronic device. Quality can be measured objectively, such as when tools are used to gauge the accuracy with which the device reproduces an original sound; or it can be measured subjectively, such as when human listeners respond to ...
Dynamic range is a measure of how small you can measure a signal relative to the maximum input signal the device can measure. Expressed in decibels, the dynamic range is 20 log (Vmax/Vmin). For example, a device with an input range of ±10 V and a dynamic range of 110 dB will be able to measure a signal as small as 10 μV.
The decibel originates from methods used to quantify signal loss in telegraph and telephone circuits. Until the mid-1920s, the unit for loss was miles of standard cable (MSC). 1 MSC corresponded to the loss of power over one mile (approximately 1.6 km) of standard telephone cable at a frequency of 5000 radians per second (795.8 Hz), and matched closely the smallest attenuation detectable to a ...
It is difficult, but very important, to match sound levels before comparing systems, as minute increases in loudness—more than 0.15 dB [11] or 0.1 dB [12] —have been demonstrated to cause perceived improvements in sound quality. Listening tests are subjected to many variables, and results are notoriously unreliable.
Loudspeaker measurement is the practice of determining the behaviour of loudspeakers by measuring various aspects of performance. This measurement is especially important because loudspeakers, being transducers, have a higher level of distortion than other audio system components used in playback or sound reinforcement.
Attempts to measure noise in audio equipment as RMS voltage, using a simple level meter or voltmeter, do not produce useful results; a special noise-measuring instrument is required. This is because noise contains energy spread over a wide range of frequencies and levels, and different sources of noise have different spectral content.
A sound level meter (also called sound pressure level meter (SPL)) is used for acoustic measurements. It is commonly a hand-held instrument with a microphone. The best type of microphone for sound level meters is the condenser microphone, which combines precision with stability and reliability. [1]