/*Dictionary of Terms*/

Frequency Response

Test Level Out 1kHz

Noise

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Electret Microphone

An electret microphone is a type of a condenser microphone (or pressure mic) that uses a diaphragm between a fixed internal volume of air and the environment. It responds uniformly to pressure from all directions and is said to be omni-directional. An electret mic's diaphram is made from a permanently-charged material which eliminates the need for a polarizing power supply (phantom power).

Omni-directional

Capable of receiving sound waves from all directions. An omnidirectional microphone's response is sphereical in three dimensions.

The wavelength of sound at 10 kHz is little over an inch (3.4 cm). The smallest measuring microphones are often 1/4" (6 mm) (the Lindos MM4 mic is 7mm) in diameter, which practically eliminates directionality even up to the highest audible frequencies. Omnidirectional microphones, unlike cardioids, do not employ resonant cavities as delays, and so can be considered the "purest" microphones in terms of low coloration; they add very little to the original sound. Being pressure-sensitive they can also have a very flat low-frequency response down to 20 Hz or below. Pressure-sensitive microphones also respond much less to wind noise and plosives than directional (velocity sensitive) microphones.

How we worked out this optimum spacing

The human ear interprets time differences between the two ears and uses them to locate low frequency sounds, up to 700Hz. Above 700Hz the phase information becomes increasingly unreliable and at 1kHz the brain relies entirely on level differences for positioning cues. For accurate phase capture the time delay must be smaller than the wavelength of the highest frequency you wish to reproduce stereo positioning for. For 1kHz the maximum delay between the channels is 1.0ms or (35cm in air).

Colouration

If the sound from a microphone sounds different in some way to the original it is said to sound coloured. A microphone that has low colouration means that it adds very little to the original sound.

Cardioid

Cardioid refers to a microphone with a heart-shaped polar response pattern. This is achieved using a diaphragm that is partially open at the front and partially closed on the back. The pressure difference between the two sides produces its directional characteristics, but as each frequency is effected differently the result is coloured to some degree.

Frequency response

Frequency response is a specification used to indicate how uniformly a piece of equipment receives or reproduces sounds from the lowest tones to the highest tones. A child is capable of hearing frequencies from 20Hz to 20kHz, as we age our ears response to high frequencies decreases.

Clipping

Clipping occurs when a system is overloaded. In the case of a preamplifier, if the gain control is set too high then as the input increases the output level will stop increasing in line with the input level. The output will sound increasingly distorted as the preamp becomes more overloaded.

European Broadcasting Union

The European Broadcasting Union is a confederation of broadcasting organisations from around the world. Its members are mostly radio and television companies which it supports by encouraging cooperation on technical issues to facilitate programme interchange and common working practices.


v5.01

  • MiniSonic and LA100 sequences can now be run from the control panel by clicking RUN. Carriage return also runs sequence.
  • Setup button now opens RunSeq window without running a sequence (LA100 only)
  • Cursor added to main graph window.
  • Redraw problems on graph fixed by re-ordering open and redraw calls in OpenBigGraph and adding a redraw command in the GotFocus event for the form. Previously if the graph window was on top of another Lin4Win window and the focus was changed from one window to the big graph window the window was drawn on top of the graph.
  • MiniSonic segments 'H' and 'L' now produce linear graphs with the correct x scales - cursor doesn't work.
  • Various changes made to ensure that the MiniSonics' function is only altered by user input.
  • The MiniSonic now starts up in what ever mode the unit is in.
  • Sequences could be previosuly be run from the SEQ menu in demostration mode - this has been disabled.
  • Toolbar buttons and menu items that are not supported by the Minisonic and/or LA100 are removed when a unit connection is established.
  • Results Heading and Comment text insertion and retreval errors have been corrected.
  • Try button fixed - ModifyHeading was not being called, heading now right aligns
  • Newpage command removed to stop an extra sheet being printed - need to test a postsript printer.
  • Linear graph cursor implemented.
  • Spin buttons work with linear graphs.
  • Cursor position memory implemented for each results page.
  • Overlay settings now work on big graph depending on their setting in a results window.
  • Save and load res file routines have been modified to work with linear graphs.
  • Read results routines unblocked.
  • Show key results option no longer causes cursor errors.