How to Make a Telephone Voice Effect in Audacity

Transforming a clean vocal recording into a vintage AM radio or telephone sound is easily achieved in Audacity through targeted equalization (EQ). This guide covers how to isolate the narrow midrange frequencies characteristic of early communication speakers, the exact frequency cuts to make using Audacity's Filter Curve EQ, and optional distortion tweaks to add authentic analog grit to your audio.

The Science Behind the Sound

Standard human hearing spans from 20 Hz to 20,000 Hz, but vintage consumer audio devices had severe technical limits. Traditional analog telephone networks (landlines) only transmitted frequencies between approximately 300 Hz and 3,400 Hz. Similarly, AM radio broadcasts severely rolled off low bass and high treble. Replicating this effect simply requires applying a "band-pass" filter that eliminates the extreme low and high ends, leaving only a boxy, nasal midrange.

Step-by-Step EQ Instructions

  1. Select Your Track: Open your audio project in Audacity. Click on the track to select the entire waveform, or drag to highlight a specific section.
  2. Open Filter Curve EQ: Navigate to the top menu and select Effect > EQ and Filters > Filter Curve EQ.
  3. Reset the Curve: Click Presets & settings in the lower-left corner, choose Factory Presets, and select Defaults to start with a flat line.
  4. Cut the Low End (High-Pass):
    • Click to create a point on the line at 300 Hz and keep it at 0 dB.
    • Create another point to the left at approximately 100 Hz and drag it all the way down to -30 dB or lower. This removes all low-end rumble and chest resonance.
  5. Cut the High End (Low-Pass):
    • Click to create a point at 3,000 Hz (3 kHz) and leave it at 0 dB.
    • Create another point at 4,000 Hz or 5,000 Hz and pull it down to -30 dB or lower. This eliminates the crispness, air, and high-frequency details.
  6. Add a Midrange Boost (Optional): Click at roughly 1,500 Hz to 2,000 Hz and raise the point by +3 dB to +6 dB. This emphasizes the tinny, nasal presence common in small speaker cones.
  7. Preview and Apply: Click the Preview button to listen to the processed audio. Adjust the cutoff points closer together for a narrower sound, then click Apply.

Extra Touches for Authenticity

To make the effect more convincing, real-world hardware limitations can be layered on top of the EQ: