View source for Passive Sonar, HF (10-500 KHz, 20 KHz Center Frequency)

A category of signature type in the Command model.

Passive Sonar, HF (10-500 KHz, 20 KHz Center Frequency) indicates the acoustic
energy signature of the target at high frequencies.

Platforms, facilities, and weapons have various compositions, construction,
and geometries that interact with the combat environment in different ways.
Signatures are the set of emitted and reflected energy properties of a given target.
Signatures will vary depending upon the energy type (such as acoustic or
electromagnetic), spectral frequency, and whether the energy is self-generated
or reflected.  Larger numbers indicate that more signal may be detected by a sensor.

Passive Sonar signatures describe acoustic energy that is self-generated and
emitted by a target.  High frequency sound will be absorbed in water more readily
than low frequency sound.  Hence low frequency sound will travel farther.
The signature is provided in decibels.

Active Sonar signatures describe acoustic energy that is reflected by a target.
This acoustic energy is typically generated by a transducer that is part of an 
active sonar sensor.  The signature is provided in decibels.

Visual signatures describe visible light that is reflected by a target.
The signature is provided in nautical miles.

Infrared signatures describe infrared radiation that is emitted and reflected by a target.
Engines and exhaust as well as reflective surfaces will increase the infrared signature.
The signature is provided in nautical miles.

Radar signatures describe electromagnetic radiation that is reflected by a target.
This radar energy is generated by a magnetrons, klystrons, etc... that are part of an
active radar sensor.  The signature is provided in decibels per square meter (dBsm).

Signature type is quantified by range or by response in decibels (dB).  A decibel is
a ratio of power or signal amplitude expressed on a base-10 logarithmic scale.  For 
signal amplitude, an increase in amplitude by a factor of 10 represents a 20 dB increase.
For power, an increase in power by a factor of 10 represents a 10 dB increase.
Negative values of decibels represent decreases and reciprocals.  For example, a large 
negative number for a target's radar signature would indicate extreme attenuation
of the reflected radar energy.  This is typical for stealth aircraft.

Note: the Baloogan Campaign Database Wiki currently displays signature metrics in a 
rectangular table, with rows of signature type and columns of target aspect.  The
annotation "nm for Visual/IR, dBsm for Radar, db for Sonar" does *not* refer to 
columns, despite the placement at the tops of columns.  Those annotations refer to
the signature units for the various rows.

Command distinguishes the signature types into:

 Passive Sonar, VLF (0-1000 Hz, 200 Hz Center Frequency)
 Passive Sonar, LF (1-5 KHz, 3 KHz Center Frequency)
 Passive Sonar, MF (5-10 KHz, 7.5 KHz Center Frequency)
 Passive Sonar, HF (10-500 KHz, 20 KHz Center Frequency)
 Active Sonar, VLF-HF (0-500 KHz)
 Visual Detection Range
 Visual Classification Range
 Infrared Detection Range
 Infrared Classification Range
 Radar, A-D Band (30-2000 MHz)
 Radar, E-M Band (2-100 GHz)