Music theory applied to car horns

I am currently working with a manufacturer that makes horns for motorcycles and automotive. We were discussing horn tone. Their sales representative had made the following statement.

"The human ear prefers to hear harmony (two or more frequencies) and hence most passenger cars and some motorcycles will have two horns on them."

We use a low note disc (360HZ, @ between F and F#) horn on some of our motorcycles. For automotive applications that use this horn an accompanying high note horn (420hz, @ between Ab and A) is used which results in harmony and a much better tone quality.

If I take the F as the root, then A is the third, so of course these naturally harmonize as you are building a chord. I found it interesting to actually apply some musical knowledge to something at work.

BC