The tympanic membrane is the last structure of the outer ear. The next part of the ear is called the middle ear, which consists of three small bones that transmit sound into the inner ear at the oval window. When the tympanic membrane vibrates, it causes motion in these three small bones, called ossicles, which then conduct the sound mechanically. The three ossicles act to amplify sound waves, although most of the amplification comes from the size of the tympanic membrane relative to the oval window. The tympanic membrane causes sound transmission in the first ossicle, known as the malleus or hammer. The malleus vibrates and transmits the sound to the next ossicle, known as the incus or anvil. The incus is then connected to the final ossicle, known as the stapes or stirrup. Their names come from their shapes. The stapes then pushes against the oval window of the cochlea, and sound moves into the inner ear.
In this activity, you can observe the motion of the ossicles in response to sounds of different frequencies and amplitudes.
To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.
On the Illustration tab, you can adjust these parameters:
Play the Sound: check to start the animation and uncheck to stop the
Frequency (Hz): adjust to see how the cochlea and basilar membrane respond to different frequencies.
Amplitude: make the sound more or less intense.
Pressing this button restores the settings to their default values and allows you to adjust speed and relative size. It also resets the counter before you can indicate if you have the objects arriving at the same time.