Integrated Science Unit 4, Chapter 13

Unit Four: Sound and Waves Chapter 13 Sound and Music 13.1 Sound 13.2 Properties of Sound 13.3 Music

Chapter 13 Learning Goals Learn how we hear sound. Learn how your brain interprets sound to understand words and music. Learn what kinds of sounds we can hear, and what kinds we cannot hear. Learn what a sound wave is and how it travels. Learn how the loudness of sound is measured. Learn the basics of acoustics as applied to the design of buildings and musical instruments. Learn to read a sonogram and how a computer recognizes spoken words. Learn what supersonic means. Learn why a musical scale sounds good, or why it sounds bad. Learn how we tell voices and instruments apart from each other.

Chapter 13 Vocabulary Terms acoustics beat/beats consonance cochlea dissonance decibel harmonics harmony musical scale pitch pressure reverberation rhythm sonogram sound supersonic ultrasound white noise

13.1 Sound What is sound and how do we hear it? Key Question: *Read text section 13.1 AFTER Investigation 13.1

13.1 Sound Sound has a frequency that we hear as higher or lower pitch. Sound has a wavelength that we can construct experiments to show. The speed of sound is frequency times wavelength. Resonance happens with sound. Sound can be reflected, refracted, and absorbed. Sound shows evidence of interference and diffraction.

13.1 Sound The eardrum vibrates in response to sound waves in the ear canal. The three delicate bones of the inner ear transmit the vibration of the eardrum to the side of the cochlea. The fluid in the spiral of the cochlea vibrates and creates waves that travel up the spiral.

13.1 Sound The nerves near the beginning see a relatively large channel and respond to longer wavelength, low frequency sound. The nerves at the small end of the channel respond to shorter wavelength, higher-frequency sound.

13.1 The range of human hearing

13.2 Properties of Sound Pressure is a measure of the force of molecules being exerted on their surroundings.

13.2 Properties of Sound More molecules per unit volume makes pressure go up. Fewer molecules per unit volume makes the pressure go down.

13.2 What sound might look like: If you could see the atoms, the difference between high and low pressure is not as great. Here, it is exaggerated.

13.2 Loudness Logarithmic scale Linear scale Decibels (dB) Amplitude 1 20 10 40 100 60 1,000 80 10,000 100,000 120 1,000,000 Every increase of 20 dB, means the pressure wave is 10 times greater in amplitude.

Common Sounds and their Loudness

13.2 The Frequency of Sound We hear frequencies of sound as having different pitch. Our ears are more sensitive to sounds between 100 and 2,000 Hz. Most frequencies that make up speech are also between 100 and 2,000 Hz.

13.2 Complex Sound

13.2 The Wavelength of Sound

13.2 Properties of Sound Does sound behave like other waves? Key Question: Does sound behave like other waves? *Read text section 13.2 BEFORE Investigation 13.2

13.3 Music What is music and how do we make music? Key Question: *Read text section 13.3 AFTER Investigation 13.3

13.3 Music: Pitch and Rhythm The pitch of a sound is how high or low we HEAR a frequency. The way we hear pitch can be affected by the sounds we heard before and after. Rhythm is a regular time pattern in a sound.

13.3 Beats Beats occur when two frequencies are close, but not exactly the same.

13.3 Consonance and Dissonance Consonance is when we hear more than one frequency and the combination sounds good. When the combination is unsettling or unpleasant, dissonance occurs.

13.3 Harmonics and "the color of sound" The same note can sound different when played on different instruments.. Instruments make mixtures of different frequencies. Compare these voices saying hello: