Does it surprise you to know that the cacophony that emanates from automobiles with booming audio systems cannot be appreciated by their drivers? The use of subwoofers in cars today not only is annoying to those outside them, but also it is not as beneficial to the users of such raucous sound equipment as they may believe.
You may have noticed that the further you are from such cars, the more you hear the boom. That’s because of the long wavelength of low frequency sounds. A subwoofer reproduces low frequency sounds in the range of 20 Hz to 500 Hz. A 20 Hz sound has a wavelength of about 56 feet (see chart below), or about four car lengths. A car is about 13 feet long. The driver, who is seated less than a car length away, cannot hear the low frequencies. Even a 60 Hz sound has a wavelength that is more than 18 feet long.
I have read a large number of complaints from owners of these systems. They complain about having to crank up the volume because they cannot hear quality sound from a system for which they paid a lot of money. They do not realize that Increasing the volume only creates more noise.
Wavelength is only part of the story. These large units usually are installed in the trunk, which is enclosed. This muffles the sound. Are there any solutions? One is to cut a hole in the trunk. Another is to have a folded horn unit instead of a direct radiating one (two photos above), so that the sound travels a longer distance before reaching the listener’s ear. This involves having the woofer in an enclosure that sends the sound through a long path before it comes out. But such enclosures are very large (as big as 36x36x36) and may not fit in the trunk.
Answer: Dilemma unresolved. The cacophony will continue unabated and the car owners will not get the full benefit of their expensive sound systems until somebody develops a folded horn speaker that will fit conveniently in the main compartment of a car.