Sound detection

How it works

Tachyon V3.2 features an on-board contact microphone to measure sound vibrations from any objects it's touching. Regular sound waves from nearby objects, such as different airsoft guns are not picked up and ignored.

There are 3 different detection modes to choose from:

  • Infrared detection - Fired BBs are detected using an IR barrel-mounted sensor
  • Sound detection - Shots are detected through sound only
  • Combined mode - Shots are counted using IR while the sound detection system is used to detect misfires

Limitations

For both Sound detection mode and Combined mode:

  • Automatic battery measurement is disabled. The battery level readout only updates when you press SELECT or RELOAD buttons
  • Bumps or impacts to the weapon can sometimes be detected as shots (Sound det. mode) or misfires (Combined mode)

For Sound detection mode only:

  • Misfires and empty shots are counted as well, since there is no way of determining if a BB actually was fired or not
  • ROF / Delay measurement function cannot be used

The quality of sound detection can be different on every individual airsoft gun. Loud and full-metal guns work best. Every time the device is mounted to a different gun (or even to a different place on the same one), the setup procedure must be performed to properly configure the detection system.

Setup

  1. Ensure that the device is mounted firmly. There must be good contact between the airsoft gun and the device, in order for vibrations to travel properly. If the part(s) the device is attached to are free to move around or wobble, the detection quality will be worsened.
  2. Start the automatic setup utility through Settings>Detection>SD Auto setup
  3. Fire single shots when "FIRE" is displayed on the screen. Release the trigger while "WAIT" is displayed. The detector is extremely sensitive at this stage and might register even small bumps or button presses as shots. If such flase trigger(s) happen, we recommend to abort and re-start the setup in order to get best end-results.
  4. Config results and statistics will be displayed on-screen after enough test shots are fired. We strongly recommend advancing into Dead time setup. This makes the detection system inactive for a very short time (Dead time) after each shot to prevent multiple detection from a single actual shot.
  5. During Dead time setup: fire in full auto (if possible) and watch the shot counter. If more shots are detected than actually fired, increase Dead time. If less shots are detected than actually fired, decrease dead time. Most often, a Dead time of around 30-120 ms will work best.
  6. Switch the detection mode to your preference in Settings>Detection>Set detection mode
  7. (Optional) Test and/or manually fine-tune the sound detection in Settings>Detection>SD Test/Man. setup (See manual setup below for more information)

Trouble-shooting

Pun intended :)

Inconsistent or no shots detected:

  • Ensure that the device is mounted firmly enough so that the vibrations from the weapon can travel into it.
  • Repeat the setup procedure or try to manually adjust settings (increasing Window tolerance can help significantly)
  • Repeat dead time setup
  • If nothing else helps, try to both increase and decrease sample length and repeat setup

More shots detected than actually fired:

  • Perform Dead time setup or manually increase it

Pressing buttons or operating weapon controls detects as shots:

  • Try to improve the device’s contact with the weapon and repeat setup
  • Try to both increase and also decrease sample length and repeat setup

Manual setup & adjustment

Navigate to Settings>Detection>SD Test/Man. setup. When a shot is fired, the sound waveform is printed on-screen. Press LEFT or RIGHT to cycle through adjustable parameters and press SELECT to edit a parameter

To register a shot, a sound wave must be above (Threshold) for exactly (Window ± Window tolerance) number of samples and enough time (Dead time) must have already passed since last detected shot.

Parameters

  • Threshold (THR): intensity level above which the sound wave must be to make a detection. This setting controls the baseline sensitivity - determines which sound waves are even considered as potential shots.
  • Window (WIND): exact number of samples (length of time) for which the sound wave must stay above threshold to make a detection (no more, no less).
  • Window tolerance (WnT): Tolerance to window value. When set, the number of samples above threshold can be higher or lower than set by the Window setting and still make a detection. This, along with the Window setting controls the final sensitivity - which sound waves are finally registered as shots.
  • Dead time (DT): time in milliseconds for which the detection system will stay inactive after a shot is detected, to prevent making multiple detections from a single shot. Setting this to '0' disables the dead time function.

Sampling rate control

The sampling rate can be regulated by adjusting the sample length setting (Settings>Detection>SD Sample length). Decreasing sample length increases sampling rate and makes the detector more sensitive to high frequency vibrations. Increasing sample length decreases sampling rate and has the opposite effect.

Whether a higher or lower sampling rate is beneficial can be very subjective. Most of the time, this setting does not need to be changed at all, but if you want to adjust the sampling rate, it is best to try both a high and low value to see which one works best. Whenever this setting is modified, the setup procedure must be repeated.

© 2021 Martin Hrehor

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