we find that
the resonance should appear in funnels whose
heights are about h 0.127m. Indeed, as one
can see in figure 5, three funnels with different R
R
1
2
ratios but all heights nearing 0.127 m provide an
Table 1. Sound level measurement results for various funnels. R1 and R2 are the radii of the edges, respectively.
Frequency 200 Hz
R1 [cm] R2 [cm] R1/R2 L1 [dB] L2 [dB] DL [dB]
0 0.58 0.58 1 119 119 0
1 2.125 0.295 7.20 118 121.7 3.7
2 3.075 0.35 8.78 118 122.2 4.2
3 4.33 0.39 11.10 117 121.3 4.3
4 5.205 0.67 7.76 116 119.2 3.2
5 2.81 0.4 7.02 119.8 122.8 3
6 3.8 0.6 6.33 119.6 122.7 3.1
7 4.21 0.69 6.10 116.7 120 3.3
8 5.62 0.7 8.02 114.7 118.2 3.5
9 2.63 0.58 4.53 119.1 121.5 2.4
10 1.665 0.4 4.16 119 121.2 2.2
Figure 4. Sound amplification DL in dB as a function of log ( ) R
R
1
2
.
Figure 5. Sound amplification by different funnels.
Funnels of heights h 0.127m resonate with frequency
674 Hz.
H Eshach and A Volfson
80 Physics Education January 2015
amplification much bigger than what is predicted
by equation (12). This demonstrates a resonance
situation well.