Chapter 10
Auditory Physiology Lab 5
To the Instructor: This is a hand-created lab designed to drive home the derivation and benefits
of the Q10 concept. I’ve left this as a rudimentary Word document so that you can modify it and
store it. Somehow, the process of plotting out the tuning curves seems to help get the idea across
better than just showing an image.
Chapter 10 Lab 5
Bandwidth and Q10
As with mean and standard deviation, center frequency and bandwidth convey different
information. Two filters can have the same center frequency but markedly different bandwidths.
Bandwidth is defined as the distance, in Hz, between points on the low and high sides of a tuning
curve. We can define any points we want, but we shall choose the points 10 dB down from the
maximum point, and we call it Q10dB, or Q10. A sharper bandwidth has a tighter resonance, to the
extreme of being a pure-tone when it is exactly 1 Hz wide! Let’s draw a resonance curve and
define the bandwidth. Plot these data and draw the curve they represent.
Frequency Intensity Frequency Intensity
Hz dB SPL Hz dB SPL
100 Hz 25 320 Hz 60
110 Hz 26 330 Hz 50
120 Hz 27 340 Hz 35
230 Hz 65 450 Hz 5
240 Hz 69 460 Hz 5
250 Hz 70 470 Hz 5
260 Hz 74 480 Hz 5
270 Hz 76 490 Hz 5
1. After you plot the data, identify the center frequency (frequency of highest sound pressure
level). Center frequency is ________Hz. Now come down on each side and identify the point
10 dB down from that point on the curve and mark them both. These are the “10 dB down
points.”
Low frequency cutoff _________; high frequency cutoff __________;
2. Now calculate bandwidth; BW = High-low ________________;
3. Now calculate Q10:Q10 = center frequency/BW = ____________;
4. Is this plot symmetrical? ______________ If not, how is it
asymmetrical?___________________________________________________
5. Does bandwidth describe this lack of symmetry? _____________
Now plot these second data points on the same graph.
Frequency Intensity Frequency Intensity
Hz dB SPL Hz dB SPL
100 Hz 5 320 Hz 20
110 Hz 5 330 Hz 15
120 Hz 5 340 Hz 10
130 Hz 5 350 Hz 5
140 Hz 5 360 Hz 5
150 Hz 5 370 Hz 5
1. Identify center frequency ______. Calculate bandwidth: _______
2. Calculate Q10:_______
3. What is the relationship between Q10 and bandwidth (relative to center frequency, of course):
_____________________________________
4. Is this second plot symmetrical? ______ Did bandwidth, center frequency, or Q10 predict this
symmetry? _________________
3
S 85|….|….|….|….|….|….|….|….|….|….|….|
u 75|….|….|….|….|….|….|….|….|….|….|….|
d 65|….|….|….|….|….|….|….|….|….|….|….|
D 55|….|….|….|….|….|….|….|….|….|….|….|
45|….|….|….|….|….|….|….|….|….|….|….|
P 35|….|….|….|….|….|….|….|….|….|….|….|
r 25|….|….|….|….|….|….|….|….|….|….|….|
15|….|….|….|….|….|….|….|….|….|….|….|
e 5|….|….|….|….|….|….|….|….|….|….|…. |
v |….|….|….|….|….|….|….|….|….|….|….|
e 0 50 100 150 200 250 300 350 400 450 500
l frequency (Hz)