Car Audio Basics

“The perceived object occasioned by the impulse or vibration of a material substance affecting the ear; a sensation or perception of the mind received through the ear, and produced by the impulse or vibration of the air or other medium with which the ear is in contact; the effect of an impression made on the organs of hearing by an impulse or vibration of the air caused by a collision of bodies, or by other means; noise; report; as, the sound of a drum; the sound of the human voice; a horrid sound; a charming sound; a sharp, high, or shrill sound.”

 If we consider that definition, sound is a lot easier to explain.  It is noise, or at the least something we sense with our ears. Clearly sound is basically nothing more that -the vibration of the air based on something that is moving.  As this article deals with car audio, we will be talking about the “movement” being our speakers.

 When using speakers to conduct your sound, it actually causes a vibration in the air which is received into the ears, and so we hear music.

A sound wave goes through a cycle of 360 degrees.  As the speaker moves forward it travels  0 degrees through one quarter of its cycle to 90 degrees. As it starts to move to rest, it then travels another 90 degrees to the 180 degree mark, before moving completely rearward to 270 degrees.

As it moves back to the rest position, it then travels the final 90 degrees to the 360 degree mark. The cycle then starts all over again and we hear the result as music. As the speaker moves up and down it travels throughout one complete cycle which is about 360 degrees. These cycles are measured in Hertz (Hz) with one Hertz meaning one cycle.

The lower the number of Hz the lower the sound is. A human can hear the sounds between 20 Hz and 20,000 Hz (also known as 20 kHz). However, we do not hear all of the sounds in the same way.  Our ears are less sensitive to sounds that are further down the scale.

When you increase the level of the low and high frequencies at lower volume levels, you will see that the volume goes up as the level of boost at these frequencies is reduced. In some instances however, loudness circuits do nothing more than boost the low and high frequencies by a constant amount.

 If you've seen a car that has an in-dash equalizer there is a very good chance that the vertical sliders were arranged in the same way as the Fletcher-Munson curve. This is sometimes called "making your EQ smile".

 The information and diagrams above has been adapted from information found at

 http://www.caraudiohelp.com/car_audio_basics/car_audio_basics.htm.

 Hopefully you now understand the basics of sound well enough for you to really see how sound travels. This information has been put together so that you can build a better car subwoofer.