1. General Engineering Polytechnic University
Laboratory #8 Vibrations, Waves & Spectra
General Engineering
Polytechnic University
9/23/2018

2. Overview Wave Equations Frequency Response Graph Objectives Procedure
Report Questions
Original Data
Graph Requirements
Closing
9/23/2018

3. Wave Equations A = amplitude = max displacement from avg
P = power = avg rate energy moves  A2
T = period = time for one oscillation = 1 f
f = frequency = # of oscillations / sec = 1 T
 = wavelength = length until wave repeats
 = speed of wave = f 
9/23/2018

4. Frequency Response Graph
Filter graphs: frequency vs. gain
Gain (db) = 20*log(Vout/Vin)
X-axis: logarithmic scale
3 dB point: output power (Pout) = 1/2 input power (Pin)
Non-ideal behavior
3 filters
High-pass filter
Low-pass filter
Band-pass filter
9/23/2018

5. Objectives
Learn about vibrations, waves, spectra, and frequency filters
Learn how to store and retrieve wave forms digitally
Record and analyze wave forms of tuning fork, notes and voices for frequency, period harmonics, and power spectrum
Identify filter 0, filter 1 and filter 2 as high-pass, low-pass or band-pass
9/23/2018

6. Procedure Capture and analyze wave generated by tuning fork
Repeat with two different notes from keyboard
Calculate amplitude, period and frequency for tuning fork and keyboard notes
Record/playback song with different voices
Fill out chart for filters 0-2 to determine which type of filter each corresponds to
9/23/2018

7. Report Questions Major difference between waveforms
Each member’s songs similar or not
Verify relationship between frequency and period
Compare frequencies obtained from FFT spectrum and calculations
Other applications using frequency filtering
Plot frequency response of each filter
Chart of tuning fork tone and keyboard note: amplitude, period, frequency
9/23/2018

8. Original Data 4 LabVIEW graphs Timefreq.vi graph of tuning fork
Timefreq.vi graphs of 2 keyboard notes
Record.vi or playback.vi graphs of different voices
EXCEL chart with 4 columns
keyboard notes / tuning fork tone
amplitude
period
frequencies (voltage/time graph = FFT spectrum)
3 EXCEL charts (1 per filter)
3 EXCEL graphs (1 per filter)
9/23/2018

9. Graph Requirements Semi-log scale Frequency response for each filter
3dB point
X-axis labeled Frequency (Hz)
Y-axis labeled Gain (dB)
Logarithmic scaling for x-axis
Label filter number and its correct filter type
XY scatter with line connecting points
9/23/2018

10. Closing Independent written report
Don’t forget to make a copy of all original data
9/23/2018