More than Meets the Ear

Continuation of Waves and Sound

Albert Einstein

• -“I want to know the mind of God,” Einstein said. “The rest are details.”

Steven Hawking

• -Today, the world’s most famous theoretical physicist, Steven Hawking, has the same goal.

• -Physics is the discovery of the truth.

• -The formulas you learn in physics are infallible. They cannot be proven wrong.

Steven Hawking

• -Steven Hawking has a motor neuron disease that progressively paralyzed every part of his body.

• -It is one of the most dreadful fates that can befall a human being

The Human Voice

• - The human voice consists of such complex waveforms, that they are only now being reproduced artificially with only moderate success.

• -Artificial voice technology, consisting of a voice synthesizer and a computer actuator, is used by individuals who have lost the ability to speak because of ailments such as throat cancer, ALS (Amyotrophic Lateral Sclerosis) and strokes.

The Human Voice

• -The field of voice engineering is expanding rapidly due to highly sophisticated microcomputer chips being developed.

• -In the near future, a robotic voice will sound very familiar to human voice.

Stephan Hawking

• -He was diagnosed with ALS at the age of 21.

• -Not given much hope of surviving more than 5 years, he is still going strong at the age of 59, making breakthrough discoveries in astrophysics and the nature of time and the universe.

Stephan Hawking

• -He uses a wheelchair, and his limited muscle control to activate a synthesizer in order to communicate.

• -He once said, “I try to lead as normal a life as possible, and not think about my condition, or regret the things it prevents me from doing, which are not that many.”

Video

• -Stephan Hawking documentary

Think-Pair-Share

• Question: Stephan Hawking is just one individual who has risen above his challenge. Do you know any other individual who did not allow their disability prevent them from pursuing their interest?

Active Sound Control

• -It consists of cancelling an undesirable noise by superposing an opposite phase noise.

-Headphones used by pilots of small planes use this technology to reduce engine noise.

Sound and Matter

Three things can happen to sound waves when they encounter different types of matter:

• 1. absorbed

• 2. transmitted

• 3. reflected

Absorption:

• - It is when sound energy is transformed into another form of energy.

• -For example, Sound Proof Rooms. The walls in sound proof rooms absorb the sound energy.

Transmission:

• -Transmission is the passing of sound energy from one medium to another at a medium boundary.

• -some sound energy is absorbed in the process.• -Transmission causes a change in the

wavelength of a wave because the sound either speeds up or slows down as it passes into the new medium.

Transmission:

• -The frequency of the wave remains the same.

• v1=fλ1

• v2=fλ2

• v1 = fλ1 = λ1

---- ----- -----

v2 fλ2 λ2

Example 1:

• Example1: A sound wave of wavelength 0.750m is travelling at 0.0 degrees Celsius when it hits a block of steel at the same temperature. What is the wavelength of the sound wave in steel if the speed of sound in steel is 5050m/s.

• (Think-Pair-Share)

Example 1: Continued

• Answer: wavelength of sound in steel is 11.4m/s.

Reflection:

2 types of reflections:• 1. reflection of a wave pulse at a fixed end has its

amplitude inverted.

-the amplitude is inverted, and the wavelength is 0.5λ.

Fig 14.7 on pg. 486

• 2. a wave pulse reflected at a free end is not invertedFig 14.8 on pg. 487

Homework or Class work:

• -pg. 487 1a.) and 1b.)-pg. 512 #13

• -Review notes from chapter 13 to today for Test on Thursday