how do ear defneders work

Huh? What is an ear defneder?

we hear sound because of the physical movement of the molecules of air. loud sounds have a larger physical movement (to prove this to yourself , take the cloth front off a loud speaker - watch the movement of the speaker as you turn up the volume. it moves more at higher volume - you may also feel pulses of air coming from the base reflex port of the speaker at high vol.)

so to make an effective ear defender, you need to attenuate (reduce) the movement of the air. Thus the type of material should be designed to reduce the flow of air. one material that you see is expanded polyurethane foam - which consists of an air filled matrix of plastic. the small pockets of air do not allow for such large movement of the air - thus making the sound quieter. double glazed windows work on the same principle - by sandwiching a thin layer of air between 2 layers of glass the deviation is reduced. Another technique is to use a solid material - where the atoms are held and thus less able to transmit the vibration - this is of course heavier. Usually a mix of techniques are used. watch out for resonance in any design. you could experiment with materials as part of the project

BTW: the electronic sound reducers that you see cause the net wound to reduce by creating a copy, 180 degrees out of phase - thus canceling the motion of the air form the original sound. but these are typically not considered ear defenders.You're welcome

Ear defenders, also known as earmuffs or ear protectors, work by reducing the amount of sound that reaches our ears. They are designed to protect our hearing by creating a physical barrier between our ears and loud noises. The basic functioning of ear defenders can be explained in a few steps:

1. Sound waves: When a sound is generated, it travels in the form of sound waves through the air. Sound waves consist of vibrating air particles that create pressure variations.

2. Sound transmission: These sound waves travel through the air until they reach our ears. They can pass through the ear canal and reach the eardrum.

3. Noise reduction: Ear defenders are designed with materials that absorb or dampen sound waves. The earcups are usually made of layers of sound-absorbing foam or other materials that are capable of reducing the intensity of the sound waves.

4. Sealing: The earcups of ear defenders are typically filled with a cushioning material that provides a comfortable fit and seals tightly against the head. This tight seal helps to block out unwanted noise from entering our ears.

5. Passive or active noise reduction: Some ear defenders are passive, meaning they rely solely on the materials and design to reduce noise. Others, known as active noise reduction or noise-cancelling ear defenders, use electronic technology to actively cancel out ambient noise. These types of ear defenders have tiny microphones that pick up external sounds and generate sound waves that cancel out the incoming noise.

By following these steps, ear defenders are able to significantly reduce the intensity of loud noises, making them safer for our ears and protecting our hearing.