What vibrates when you play bass drum?

Answer 1

Everything. (If you do it properly!)

Edit, considerably after that first line: I have to admit that the answer was more tonge-in-cheek than I intended, so here's an answer taking the question at face value.

A bass drum consists of a shell (or hoop) of relatively thin wood, two heads (originally of skin, now usually of a synthetic substitute membrane) and two rims with connecting hardware used to hold the heads in place on the shell. This results in a large 'drum' with the skins free to vibrate. Most often, a bass drum also has a hole or vent in the shell somewhere, which allows the air inside the drum to exit or enter as the heads may vibrate in such a way as to change the physical size of the air chamber.

When you strike the bass drum, it is with a wooden or padded stick called a Beater. Often, there will be a different sized pad at each end of the beater, allowing different effects. However, Bass drums come in many sizes and configurations, and are struck with many different kinds of beaters which can seem quite odd, if you are used to only a limited variety.

The bass drum is sounded by striking the head with the end of the beater. Striking dead-center on the head tends to make a more muffled sound than striking it near the rim. When a drum, in general, is struck on the head, the head vibrates, and the immediate vibration is regulated by the stiffness with which the edge is bound to the shell, the tension on the skin caused by the shell pressing into the head at the edges, the location on the head where it is struck, and the type of beater and how it is held. There are a lot of variables there, but the results are fairly obviously a base-drum sound.

Immediately after the head is struck, as it starts to vibrate, the sound is modified and affected by the airspace between the heads, which transfers energy from the one head to the other, taking vibration itself, depending on its volume, the size and depth of the vent hole, and other factors. The 'length' of the bass drum sound is determined by how long the heads vibrate.

So when the bass drum is struck, the heads vibrate, and the air within the drum vibrates. The shell vibrates as well, and because of the frequency of the tones which make up the sound and the power which can be imparted to the sound, everything else vibrates. All musical instrumets, at some point, have to vibrate the air, and in so doing, vibrate the ear's membrane and bone-structure to transmit the sound into the cochlea, because without this, the sound of the instrument would not be heard. But the bass drum is generally made and tuned to be very forceful, and when it is struck, its affects can often be felt as well as heard. Hence, everything vibrates.

Answer 2

what vibrates when you beat a drum

Answer 3

The drum heads and the drum shell.

Answer 4

strings