PHY 3620, Section 2Physics of Sound & MusicDr. Jeff Loats

Bring up an ID (any) to borrow an iClicker for the day.

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Acoustics

Psychological acoustics

Speech and hearing

Architectural acoustics

Digital music

Sound reproduction and re-enforcement

Musical acoustics

3Our Focus: Musical AcousticsProduction

Propagation

Perception

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Math & Critical Thinking

Consider:

Scales and musicMath and science

Concepts at all times, math when needed

• Basic algebra will be used regularly

• At most we will deal with square roots and logarithms

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Dr. Jeff Loats

www.msudenver.edu/physics/loats

Office: NC 3123F

Email: jeff.loats@gmail.com

Office hours posted on my website

Email is the best way to reach me

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Materials & Tools

Textbook (required):The Physics of Sound, 3rd ed. by Richard E. Berg & David G. Stork

iClicker (buy at book store)

Calculator! (get one, bring it every day)

7Warm-Up Assignments (Online)Online assignments due before class, about class

Two purposes:

You do reading and get a first exposure

I learn where you stand and customize class

Graded on thoughtful effort, NOT correctness

Responses will be quoted (anonymously) in class

Questions are available 2-3 days before class

Due at 10:00 p.m. the night before each class

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Homework & Connections

Homework–Due weekly (usually Thursdays by 5 PM)–Counts for 25% of your final grade (BIG)!

Connection activities:–Occasional assignments (3+)–Various activities: Hearing tests, reaction papers,

virtual experiments, etc.–Good writing is expected

(grammar, citations, etc.)

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Website

www.msudenver.edu/physics/loats

Course Information in three parts

PowerPoint Lecture Files

Homework assignments & solutions

Connection activities

Other Handouts

Link to UserID Roster system!

Link to WarmUps!

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Components & Grading

Exams (mini, 1&2) 30%Comprehensive final 15%Homework 25%Connections 15%Warm-Ups 10%Disc. Participation 5%

Note the expanded A range.

The top and bottom 1% of B, C and D get +/-.

Grading Scale90 - 100% = A85 - 90% = A-75 - 85% = B65 - 75% = C55 - 65% = DBelow 55% = F

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Participation

Discussion questions using iClickers

Participation counts (correctness doesn’t)

Cannot be made up

Earn two “freebies” at the end of the term…

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Using iClickers

Power button (auto-off after a while).

If “Vote Status” indicator flashes ,your response was recorded and confirmed!

If “Vote Status” flashes , your response was not received OR the system is not active.

Resubmit if you like, it only keeps the last one.

Your remote uses radio waves, no need to point it.

GREEN

RED

Have you used a classroom response system before?

A) Yes, hardware (iClickers, etc.)

B) Yes, software (PollEverywhere, TopHat, etc.)

C) Nope

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What is your class standing?

A) Freshman

B) Sophomore

C) Junior

D) Senior

E) Other

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What kind of musical experience do you have?

A) I am an appreciator, but I don’t play or sing.

B) I actively play an instrument or sing, but it isn’t my major.

C) I am a music major.

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Have you had any physics before?

A) Not a bit

B) Yes, about 1 semester

C) Yes, about 1 year

D) Yes, more than 1 year

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Which best describes the highest level of math you have successfully taken?

A) Remedial math of some kind

B) High school algebra

C) College algebra.

D) College trigonometry or higher.

E) I am a master of all things mathematical.

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Science and Music?

Most of the oldest known musical instruments are 20 to 25 thousand years old.

Current record holder: A 35,000 year old flute found in Germany.

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Science and Music?

Most of the oldest known musical instruments are 20 to 25 thousand years old.Current record holder: A 35,000 year old flute found in Germany.

Until “recently” the study of sound and music was part of mathematics.

Today’s science/music division would have been considered very strange.

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Ancient Acoustics

The Pythagoreans believed that math, music and astronomy had a mystical connection: They were all governed by the ratios of whole numbers.

Here an artist blended ancient Greek ideas with Christian beliefs by renaming Pythagoras once.

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Ptolemy (2nd century C.E.) came up with a model for the solar system based on this idea.

This idea was strong enough to last 1500 years before Copernicus asserted that the sun is the center of the solar system, not the Earth.

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Progress?

Copernicus (15th century) disagrees with Ptolemy's theory … the sun is the center of the solar system!

Finally, Kepler (16th century) tries to prove that there is geometrical order in the solar system, but discovers that there is not. (Ethical science!)

Since then (roughly), science and musical theory have drifted apart, until we no longer treat them as the same subject at all.

So here we are, physicists rarely take music theory and musicians usually avoid physics…

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Our Physics Toolbox

Position, length or distance (symbols x, y, l, d)• Measured in meters.• We use +/- to indicate direction.

Time (symbol t)• Measured in seconds.

Velocity or speed (symbol v)• Not the same thing (velocity includes direction).• Again +/- can indicate the direction of travel.

These are related: d vt

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Students have developed a robot dog and a robot cat, both of which can run at 8 mph and walk at 4 mph.

A the end of the term, there is a race!

The robot cat is programmed to run for exactly half of its racing time. The robot dog is programmed to run for exactly half the racing distance.

Who wins?

A) The cat! B) The dog! C) They tie!

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Our Physics Toolbox

Acceleration (symbol a)• Acceleration measures how quickly

your velocity changes (a tough concept).• Technically any chance in velocity is acceleration,

and the term decelerate isn't used.Mass (symbol m)• Not the same as weight, mass is a measure of how

much "stuff" there is in an object.• Think about being in deep space where

everything is weightless.

va

t

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Our Physics Toolbox

Density (symbol ρ, the Greek letter "rho")• Density is a notoriously difficult

concept, combining mass and volume.• Mass per unit length (symbol W in this book) will

be important when we talk about stretched strings.

Force (symbol F) – "A push or a pull"• Measured in newtons (N), for good reason. The

English system measures force in pounds (lbs).• Weight is the force of gravity caused by the Earth,

pulling everything towards its center.

m

V

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Our Physics Toolbox

Pressure (symbol p)

• Pressure tells us how a force is spread out; force divided by area.

• Important to us, because sound itself is a "pressure wave" or a "compression wave".

• The atmosphere pushes in on you with a force of 14.7 pounds on every square inch if your body (100,000 newtons on each square meter).

• Rather than saying N/m2 we call it a pascal (Pa) in honor of Blaise Pascal.

FP

A

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Musical Toolbox – Intervals

Our most fundamental musical idea: The musical interval.A musical interval describes the relationship between two tones or notes.Examples: C to G is called a fifthE to B is also a fifth

The relationship between each member of the pairs is the same. The relationship sounds the same in both cases.

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Weekly Music Practice

We won’t intervals much for a few weeks, but we will prepare by doing a few music theory questions each week.

Pages 368 and 369 have what you need to handle all the music theory parts of the course.

To get you started:

–A “half-step” is the interval between adjacent keys on the piano (no skipping black keys).

–An octave (much more later) is the interval between notes that have the same letter name.

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Coming up…Thursday (8/21) → 1.1 – 2.3

Your first WarmUp (for Thursday’s class) is due Wednesday night by 10:00 PM

1st homework (Due Tuesday by 5 PM):Ch. 1: Q: 2, 6, 8 P: 3, 5, 6 + Theory (ONLINE)

Get an iClicker! Register it eventually…