Troubleshooting audio for TwoToneDetect (TTD) and Live Audio requires a methodical approach because the software relies on a consistent, "clean" analog signal to decode digital tones. Whether you are running on Windows or a Raspberry Pi, the signal path remains the same: Source → Cable → Sound Card → Software.

Phase 1: Check the Audio Source (The Radio/Scanner)

Phase 2: Inspect Hardware & Connections

Phase 3: Operating System Audio Settings

Phase 4: TwoToneDetect Software Tuning

Summary Checklist

Deep Dive into Interference and static

Here is a universal troubleshooting guide to help you isolate and fix audio issues.

Phase 1: Check the Audio Source (The Radio/Scanner)

Before touching the computer, ensure the signal leaving your radio is clear and at the correct level.

• Listen via Built-in Speaker: Unplug the audio cable from the radio. Does the audio sound clear to your ear? If it’s static-filled or weak, TTD  & Live Audio won't be able to decode it.

• Volume Level (The "Goldilocks" Zone): 

  • Too High: If the volume is too loud, the signal 'clips' (distorts), and TTD or Live Audio sees it as flat noise. In the TTD Debug log, if the volume column shows 30,000+, turn the radio volume down to 15-25%.

  • Too Low: If the volume is too low, the signal won't break the "Audio Squelch" threshold in TTD. The TTD Debug log will indicate that the 'threshold is too low'.

• Disable Alerts: Ensure the radio's "button beeps" or "vibrate on alert" settings are OFF. These sounds interfere with tone detection.

• Audio Input Source:   Check your TTD GUI program or Live Audio settings for the AUDIO INPUT DEVICE.  Ensure that you have the proper option selected.  On a Windows OS, you don't want to utilize the Microsoft Sound Mapper, if there is a better option.

  • If you do use the Microsoft Sound Mapper, you may want to ensure that your computer isn't used for any other audio functions, as this could detract from the TTD program.

Phase 2: Inspect Hardware & Connections

Physical interference is the most common cause of "hum" or "buzzing" in TTD logs.

• The Cable: Use a high-quality, shielded 3.5mm male-to-male audio cable. Unshielded cables act like antennas and pick up electronic noise from nearby power bricks or monitors.

• Physical Separation: Keep the radio and the computer as far apart as the cable allows. Digital noise from a Raspberry Pi or PC motherboard can bleed into the radio’s receiver.

• Ground Loops: If you hear a constant low "hum," it may be a ground loop caused by the radio and computer being plugged into the same power strip.

  • Quick Fix: Try running the radio on battery power (if possible) to see if the hum disappears.

• The Sound Card: * Windows: Many internal mic jacks are "mono" or have "auto-gain" that ruins TTD's detection. A cheap USB Sound Card is often more reliable.

  • Raspberry Pi: The Pi does not have a native "Audio In" port. You must use a USB Audio Adapter. Ensure it is firmly seated in the USB port.

Phase 3: Operating System Audio Settings

Even if the hardware is perfect, the OS can "process" the audio and break the tones.

For Windows Users:

1. Disable "Audio Enhancements": Go to Sound Settings > Input Device Properties. Disable "Equalizers," "Noise Suppression," or "Acoustic Echo Cancellation." These features treat tones like "background noise" and try to filter them out.

2. Privacy Settings: Ensure "Allow apps to access your microphone" is toggled ON in Windows Privacy settings.

3. Default Format: Set the Sample Rate to 1 channel, 16-bit, 44100 Hz (CD Quality).

For Raspberry Pi Users:

1. Check PulseAudio/Alsamixer: Run alsamixer in the terminal. Ensure the "Capture" level for your USB device is not muted (indicated by "MM") and is set to a reasonable gain (usually around 50-70%).

2. Device Index: If TTD isn't "hearing" anything, the OS might have assigned the USB card a different index (e.g., hw:1,0). Verify this with arecord -l.

Phase 4: TwoToneDetect Software Tuning

Once the OS sees the audio, you must tune TTD to "listen" correctly.

• Select the Correct Input: In the TTD GUI, ensure the Audio Input Device matches your hardware.

   

• Set the Squelch: * Watch the "Audio Level" bar.

  • Set the Audio Squelch slider just slightly to the right of the resting noise floor.

  • When the radio is silent, TTD should display "No Audio."

     

• Check the Debug Log: Click View Debug Info.

  • The first column is the frequency.

  • The second column is the volume.

  • If you see random frequencies popping up constantly while the radio is quiet, your Squelch is too low or you have electronic interference.

Summary Checklist

Deep Dive into Interference and static

When using a Radio/Pager/Scanner that plays its own sound when your agency is “toned”. Turn these additional alert sounds OFF. This additional sound from the Hardware is likely interfering with your TTD or Live Audio program hearing the broadcasted A Tone and B Tone come through the hardware itself.

• THIS INCLUDES A VIBRATION. If your hardware vibrates when a call is received, turn the Vibration OFF.
• When using a Radio/Pager/Scanner that has a charging “cradle”, TTD and Live Audio will likely pick up a quiet “hum” of white noise from the “cradle” charging process. You will want to try the device when it is NOT in the “cradle” to see if the “interference” goes away.
• PLACEMENT- you will want to make sure that your hardware and your computer running TTD or Live Audio are as far apart as your Auxiliary Audio Cable allow.
• Ensure that your Auxiliary Audio Cable is “shielded” from outside interference. If not, it may pick up electronic sounds and static like it was itself an antenna.
• If your VOLUME column of the Debug Info is 30,000+, turn your device’s volume knob down, to 15-30% of the maximum on your device. 

There are a few ways to manage interference:

(not in order or preference)

1. Find the cause and eliminate it (other computers/servers/devices/appliances)

2. Adjust the Squelch to stop the static (radio transmissions still need to come through)

3. Better wire management (no tangles, braids, twists, wires draped over other appliances/devices)

4. For your reading pleasure, see this link and consider the possibility that the static is environmental (your rooms wiring/connections/wall plug usage)

-- Article about HUMs/STATIC --