You can make your audio sound muffled using a built-in equalizer in Adobe Audition. Muffled audio contains more of the lower-end frequencies as these are much better capable of passing through objects compared to higher-end frequencies. Therefore, we’ll cut out higher-end frequencies using an equalizer to achieve a muffled audio quality such that you would hear when speaking from under a duvet or in another room.
Here’s a step-by-step guide:
- Select the part of your audio recording you want to be affected
- Go to Effects->Filter and EQ->Scientific Filter
- Choose Types: Butterworth and Modes: BandPass
- Set Order: 3, Cutoff: 0
- Set High Cutoff to around 1200Hz
You can control High Cutoff to adjust how muffled your audio will become. Settings it lower will make your audio more muffled. Try different values to check what works best for you.