How to Create an Underwater Effect in Audacity

Creating an underwater or muffled audio effect is a simple process in Audacity that relies primarily on low-pass filtering. Water naturally absorbs high-frequency sound waves much faster than low frequencies, causing sounds heard beneath the surface to appear dull, warm, and indistinct. By using Audacity’s built-in Low-Pass Filter to eliminate treble and midrange frequencies, you can simulate this submerged sensation in just a few clicks. This guide walks you through importing your track, applying the correct filter parameters, and adding subtle atmospheric enhancements for a convincing result.

Step 1: Import and Select Your Audio

1. Launch Audacity.
2. Go to File > Open or File > Import > Audio to load your target audio file.
3. Select the section of audio you want to process using the Selection Tool, or press Ctrl + A (Windows) or Cmd + A (Mac) to select the entire track.

Step 2: Open the Low-Pass Filter

1. Click on the Effect menu in the top toolbar.
2. Navigate to EQ and Filters and select Low-Pass Filter. (In older versions of Audacity, Low-Pass Filter is located directly in the main Effect dropdown list.)

Step 3: Configure the Filter Settings

The Low-Pass Filter works by allowing frequencies below a certain threshold to pass through while reducing or cutting frequencies above it.

• Cutoff Frequency (Hz): Set this value between 400 Hz and 800 Hz. A setting around 500 Hz provides a standard, deep underwater muffle. Lowering the number closer to 300 Hz creates a much deeper, denser submergence, while raising it to 1000 Hz results in a lighter, partially submerged sound.
• Rolloff (dB per octave): Choose 24 dB or 36 dB. A steeper rolloff cuts out the higher frequencies more aggressively, providing a cleaner and more distinct underwater illusion without lingering high-end hiss.

Click Preview to listen to the result, adjust the cutoff frequency as needed, and click Apply.

Step 4: Add Reverb (Optional)

Sound waves bounce uniquely in water, so adding a small amount of reverb enhances the realism of the effect.

1. With the track still selected, go to Effect > Delay and Reverb > Reverb.
2. Set Room Size to roughly 40%–60%.
3. Increase the Wet Gain to around -6 dB and lower the Dry Gain to -3 dB to emphasize the diffuse sound reflections.
4. Set Damping high (around 70%–80%) to ensure the reverb itself does not introduce unwanted high frequencies.
5. Click Apply.

Step 5: Compensate for Volume Loss

Removing high and midrange frequencies naturally reduces the overall perceived volume of the track.

1. Go to Effect > Volume and Compression > Amplify (or Normalize).
2. Set the New Peak Amplitude to -1.0 dB or use Amplify with standard settings to bring the volume back up to an audible level without clipping.
3. Export your finished audio by navigating to File > Export Audio.