Summarize: What type of changes did we see when the instruments were vibrating?

92R How do the vibrations of the sound source compare for louder vs softer sounds?

To study the vibrations more closely, we will look at a larger object that will vibrate How is this like the guitar string and tuning fork? Investigation Set up: Meter Stick Index Card BOX Sensor ➔ The vibrations in a large scale object might be easier to observe and see.

Vibrations happen really fast Vibrations happen really fast...to help study we will use a motion sensor: How does the sensor work: What does the y- axis represent? What does the x- axis represent When does the line go up? Down? Move fast vs slow? If it is stationary? ➔ It goes up because that shows you are getting farther away from the detector. ➔ The y-axis represents the distance the object is from the detector. ➔ The y-axis is in meters. ➔ The x-axis represents the time since the detector was started. ➔ The x-axis is in seconds → fast= steeper and slow equals more gentle

How does softer vs harder hit compare? Softer Hit: Harder Hit:

How does softer vs harder hit compare? (any patterns you notice? Hit with more force (louder) Hit with less force (softer) .8 .8 Position (m) .6 Position (m) .6 .4 .4 .2 .2 1 2 3 4 Time 1 2 3 4 Time

92R Patterns of waves: ➔ There is an S-shape or wave-shaped pattern in both graphs; the pattern repeats. ➔ The spacing between the high and low points gets smaller as time goes on. ➔ The spacing between the high and low points (y-values) was less in the first graph when the rod was struck softly. ➔ The time between a high point and a low point appears to be the same within each graph and between graphs.x ➔ The time between two high points appears to be the same within each graph and between graphs.

Characteristics of Waves: Amplitude: The height or depth of a wave from average level. Skip a few lines

Frequency How often a wave pattern repeats itself Skip a few lines

Wavelength: The distance between the two tops in a series Wavelength

93RHow do the graphs help us to understand… “How do the vibrations of the sound source compare for louder vs. softer sounds? Hit with less force (softer) Amplitude: Frequency (waves per second) Hit with more force (louder) Amplitude: Frequency (waves per second) .8 .8 Position (m) .6 Position (m) .6 .4 .4 .2 .2 1 2 3 4 Time 1 2 3 4 Time

Characteristics of Waves: Amplitude: The height or depth of a wave from average level. High amplitude= louder sound Low amplitude= softer sound

Frequency How often a wave pattern repeats itself Frequency of the vibrations does not change when only the volume of the sound source changes.

? ? 94R Sound Source ear/detector “Sound” moves Force Impact or Push/Pull ? Instrument moves/ bends back and forth ?

How can we update our model? 94R Sound Source ear/detector “Sound” moves Force Impact or Push/ Pull ? Instrument moves/ bends back and forth Larger distance deform = larger amplitude Ear hears louder

How else does sound differ?