1. -ِ Acoustics -Arch 353 -Dr. Abdelrahman Elbakheit -References الصوتيات, د. سعود صادق حسن.1

2. Sound and hearing mechanisms: - The study of subjective sound properties that can not be measured or quantified but can be statistically studied through samples of people. Components of the human ears: -Our ears is composed of three main sections. Outer Ear, Middle Ear and Inner Ear. Outer year: open to the air and is composed of the outer Shape (Pinna) Inner tube and ear drum. Middle ear: it has the three bones (ossicles). It is connected With the inner ear through the oval window and To the outside through Eustachian Tube. Inner ear: has to connection to the outside Air. It has semi-circular canals and the cochlea. The canals are perpendicular to each other, responsible for our equilibrium. The Cochlea is about 4cm in length, divided longitudinally into canals filled with a liquid and is connected with hearing nerves Connected to our brains.

3. Ear Sensitivity: The ear is sensitive for frequencies from 20-20000 HZ. In a Logarithmic response. From this range our speech Is located around 500-4000HZ. Which is the range we tend To loose first. Threshold of feeling is 120 Decibel. Threshold of pain is 130 Decibel. Sound Pitch: It is a name for levels of frequencies. High pitch sound is sound with high frequency. Low pitch sound with low frequency. Sound Masking: Any sound to be heard properly it has to be 10-20 db, above the background sound. Low frequency sound has the potential to mask high frequency sounds. Therefore in auditoriums it is important to stop low frequency sounds not to be allowed because they mask speeches, which are considered high frequency.

4. .