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  2. Hearing protection fit-testing - Wikipedia

    en.wikipedia.org/wiki/Hearing_protection_fit-testing

    Hearing protector fit-testing is a method that measures the degree of noise reduction obtained from an individual wearing a particular hearing protection device (HPD) - for example, a noise canceling earplug or earmuff. Fit testing is necessary due to the fact that noise attenuation varies across individuals.

  3. Noise measurement - Wikipedia

    en.wikipedia.org/wiki/Noise_measurement

    Noise measurement can also be part of a test procedure using white noise, or some other specialized form of test signal.In audio systems and broadcasting, specific methods are used to obtain subjectively valid results in order that different devices and signal paths may be compared regardless of the inconsistent spectral distribution and temporal properties of the noise that they generate.

  4. Tube sound - Wikipedia

    en.wikipedia.org/wiki/Tube_sound

    Tube sound (or valve sound) is the characteristic sound associated with a vacuum tube amplifier (valve amplifier in British English), a vacuum tube-based audio amplifier. [1] At first, the concept of tube sound did not exist, because practically all electronic amplification of audio signals was done with vacuum tubes and other comparable ...

  5. Motorboating (electronics) - Wikipedia

    en.wikipedia.org/wiki/Motorboating_(electronics)

    In electronics, motorboating is a type of low frequency parasitic oscillation (unwanted cyclic variation of the output voltage) that sometimes occurs in audio and radio equipment and often manifests itself as a sound similar to an idling motorboat engine, a "put-put-put", in audio output from speakers or earphones.

  6. Korotkoff sounds - Wikipedia

    en.wikipedia.org/wiki/Korotkoff_sounds

    However, there has recently been a move towards the use of the fifth Korotkoff sound (i.e. silence) as the diastolic blood pressure, as this has been felt to be more reproducible. [9] For paediatrics, there has been controversy regarding whether to use auscultation of the fourth or fifth Korotkoff sound as an indicator of diastolic pressure ...

  7. Valve audio amplifier - Wikipedia

    en.wikipedia.org/wiki/Valve_audio_amplifier

    A valve audio amplifier or vacuum tube audio amplifier is a valve amplifier used for sound reinforcement, sound recording and reproduction. Until the invention of solid state devices such as the transistor , all electronic amplification was produced by valve (tube) amplifiers.

  8. Steam whistle - Wikipedia

    en.wikipedia.org/wiki/Steam_whistle

    The whistle consists of the following main parts, as seen on the drawing: the whistle bell (1), the steam orifice or aperture (2), and the valve (9). When the lever (10) is actuated (usually via a pull cord), the valve opens and lets the steam escape through the orifice. The steam will alternately compress and rarefy in the bell, creating the ...

  9. Heart click - Wikipedia

    en.wikipedia.org/wiki/Heart_click

    The mitral valve in cases of mitral stenosis may open with an opening snap [1] [2] on the beginning of diastole. Patients with mitral valve prolapse may have a mid-systolic click along with a murmur, referred to as apical late systolic murmur. [3] Early systolic clicks may also be present in some patients. [4]