An acoustics engineer measures the performance of a prototype polymer foam panel designed to damp industrial noise. A constant-intensity sound source is placed on one side of the panel, and the sound pressure level transmitted through the panel is recorded on the other side at various frequencies.
| Frequency (Hz) | Transmitted Sound Level (dB) |
|---|---|
| 250 | 74 |
| 500 | 62 |
| 1000 | 51 |
| 2000 | 43 |
| 4000 | 29 |
| 8000 | 38 |
State the reason why 4000 Hz is identified as the frequency at which the polymer foam panel is the most effective sound insulator.