A Quick Telephone Audio Effect

[ This tip was written in response to a request from one of my Final Cut classes on how to create this effect. ]

NOTE: FCP X includes a telephone effect filter, which earlier version of Final Cut Pro, and Soundtrack Pro, do not.

Here’s a fast way to create a quick audio effect to make your dialog sound like it is coming from a telephone.

First, a quick background. In order to squeeze more phone circuits into a single wire, the phone company limits the frequency response of phone calls to between, roughly, 350 cycles and 3,500 cycles per second.

Since normal human hearing ranges from 20 cycles to 20,000 cycles per second, the limited frequency response in a telephone call gives it it’s unique sound.

So, in order for us to create a similar effect, we need to limit the frequencies of our dialog. This picture illustrates what I’m talking about. While the total frequency response of human hearing is 20 – 20,000 cycles per second, the portion that we want to create for our telephone effect is only between 500 and 2,500 cycles per second.

We’ll use two audio filters applied to the same clip to remove these unwanted frequencies.

1. To do this, select your audio clip in the timeline and double-click it to load it into the Viewer.

 

2. Now, assign a high-pass filter to the clip. A High-Pass filter only allows frequencies ABOVE a certain value (500 cycles per second in our example).

 

3. Next, assign a low-pass filter to the clip. A low-pass filter only allows frequencies BELOW a certain value (2,500 cycles per second in our example). This frequency “chopping” is more severe than a normal telephone, but it helps to make the aural effect more believable.

 

4. Click the Filters tab at the top of the Viewer and set the frequency values equal to this illustration.
5. Play your clip.

Ta-DAH! Instant telephone effect.

 

UPDATE – Nov. 27, 2007

Ben Balser writes:

Your current issue (I love this newsletter) has a letter from Trent Anderson about how to get the telephone effect.

In STP 2, if you apply Process > Effects > EQ > Channel EQ, there are several presets that will get you started on very nice telephone (or 2-way radio) sound effects. In the control window of that effect go to Show Presets > 07 EQ Tools. In that category there are: Megaphone EQ, Phone Filter Notch, Phone Filter Wide Band, and Telephone EQ.

I’ve been finding these very good places to get that effect from. If any is not perfect for what you personally want, simply apply the one that is a closest match, tweak the controls (never be afraid to experiment with these filter controls), once you have what you want, you can add it as your own User Preset for future reference, or to apply to other sound clips in the same FCP project. It makes getting the telephone/radio effect much faster and easier and better sounding. Even for an old sound guy like me who can do it manually in my sleep. Gotta love them Presets in STP!

Larry replies: Thanks, this is another way to do the same thing.

---

Bookmark the permalink.