Micro Speaker Dynamic Receiver speaker transducer

Micro Speaker/Dynamic Receiver

Speaker & Receiver structure and theory introduction

　　Sound is simply a wave of varying air pressure. These pressure waves cause a thin membrane in the ear to vibrate and the brain interprets these vibrations as sound. When the acoustic wave is propagated by compressible medium, it will cause pressue diturbance to produce sound.

Speaker & Receiver

　
The rate of change in Sound Pressure Level is measured by frequency.A normal young man can hear sound frequency range from 20Hz to 20KHz, that is audio. However, speech is human's sound that range from 100Hz ~ 4KHz.

　　There are three major factors to consist the sound: sound loudness, sound sharpness and sound quality. Generally, A normal human ear can perceive a sound frequency from the range of 20 Hz to 20 KHz.

　　However, our ears respond better at mid range frequencies and also, they have higher sensitivity on certain frequencies than others. This explains why a given sound pressure level seems "louder" at 5000 Hz than the same sound pressure level at 50 Hz. In order to provide a balancing effect due to this phenomena, an A - Weighting curve is employed, so that the measured sound pressure level is adjusted to a way similar to how we hear.

─：Actual Human Sensation
------：Simulated Human Sensation

Construction：

　　From the below picture, micro speaker can be mainly divided into three parts. Firstly, the vibration system contains cone paper, damper and voice coil. The magnetic flux part has magnet, yoke and center pole. And frame, gasket, dust cap and terminal consist to the body.

1. Frame
2. Yoke
3. Plate
4. Magnet
5. Diaphragm
6. Voice Coil
7. Terminal
8. Non-woven Fabric

Operation Principle：

a. Moving Direction

b. Fleming Left Hand Rules

c.	Vibration in One Domain
	(1) The moving model of speakers can be simulated to a spring with a mass fixed on ceiling. (2) or be simulated to a mass moving in horizon by S.H.M.