A goniometer is often included in analog audio

Sound

Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...

 equipment to display a Lissajous figure which shows the amount of stereo

STEREO

STEREO is a solar observation mission. Two nearly identical spacecraft were launched into orbits that cause them to respectively pull farther ahead of and fall gradually behind the Earth...

 (that is, phase differences) in a dual-channel signal. It allows the sound technician to adjust for optimal stereo and determine the makeup of errors such as an inverted signal. Many goniometers also provide a VU

VU meter

A VU meter is often included in audio equipment to display a signal level in Volume Units; the device is sometimes also called volume indicator ....

 or PPM

Peak programme meter

A peak programme meter is an instrument used in professional audio for indicating the level of an audio signal.There are many different kinds of PPM. They fall into broad categories:...

 meter as a secondary function. A goniometer adapted for surround metering is called a 'jellyfish display'. This term was coined by DK-Technologies A/S from Denmark.

Function

Its function is to plot a signal on a two-dimensional area so that the correlation between the two axes (audio channels, or phases

Phase (waves)

Phase in waves is the fraction of a wave cycle which has elapsed relative to an arbitrary point.-Formula:The phase of an oscillation or wave refers to a sinusoidal function such as the following:...

) becomes apparent.

The channels are plotted on diagonal axes; a left-channel-only signal would form a diagonal line running top-left to bottom-right and a right-channel-only signal would form the opposite diagonal running top-right to bottom-left. A signal on both channels would provide components on both axes and thus expand the plot into two dimensions: a mono signal would produce a straight line angled according to balance; whereas a stereo signal, being asymmetrical, would produce a jittery and fluffy-looking ball (see image).

An audio technician would typically start a session by adjusting the equipment (usually with a 1 kHz mono tone

Musical tone

A musical tone is a steady periodic sound. A musical tone is characterized by its duration, pitch, intensity , and timbre . The notes used in music can be more complex than musical tones, as they may include aperiodic aspects, such as attack transients, vibrato, and envelope modulation.A simple...

) so that the output produces a vertical plot line. If one channel were phase-inverted, it would result in the plot line being a horizontal instead of vertical, a sure sign of problems. As for mono signals, a half-inverted signal would be reduced to (near) silence.

The persistence of a CRT display is a desired effect on goniometers because the signal display is very dynamic, and the overall shape or envelope of the signal is the object of interest. In fact, good digital and software goniometers provide artificial and even user-adjustable persistence.

The goniometer proves useful because it provides very dense information in an analog and surprisingly intuitive form. From the display, one can get a good feel for the audio levels for each channel, the amount of stereo and its compatibility as a mono signal, even to some degree what frequencies are contained in the signal. Experts may even be able to determine the probable arrangement of microphones when the signal was recorded.

See also

• VU meter
  VU meter
  A VU meter is often included in audio equipment to display a signal level in Volume Units; the device is sometimes also called volume indicator ....
  
  
• Peak programme meter
  Peak programme meter
  A peak programme meter is an instrument used in professional audio for indicating the level of an audio signal.There are many different kinds of PPM. They fall into broad categories:...
  
  
• Mixing console
  Mixing console
  In professional audio, a mixing console, or audio mixer, also called a sound board, mixing desk, or mixer is an electronic device for combining , routing, and changing the level, timbre and/or dynamics of audio signals. A mixer can mix analog or digital signals, depending on the type of mixer...
  
  
• PPM
  Peak programme meter
  A peak programme meter is an instrument used in professional audio for indicating the level of an audio signal.There are many different kinds of PPM. They fall into broad categories:...
  
  
• Goniometer
  Goniometer
  A goniometer is an instrument that either measures an angle or allows an object to be rotated to a precise angular position. The term goniometry is derived from two Greek words, gōnia, meaning angle, and metron, meaning measure....