Reflecting surfaces cannot create new frequencies in ordinary echoes
Evidence
Can echoes change the pitch of the original sound? An object can reflect high-frequency sound with greater or lesser efficiency than low-frequency sound, but it can do nothing to introduce new frequencies that aren’t already present, unless the object itself is set to vibrating at these new frequencies. This is theoretically possible, through nonlinear response. It is certainly not a common occurrence, and is not expected to happen for most audible sounds, which are, after all, very feeble conveyers of energy. — Eric J. Heller, Why You Hear What You Hear- An…, 2629
Categorization
Category: Causal Relationships
Related
- Reflections cannot introduce frequencies not present in the original sound (similarity 0.94)
- Echoes rearrange spectral energy without changing its total (similarity 0.85)
- Reflected sound waves interfere with direct waves to create frequency peaks and dips (similarity 0.84)
- The fixed energy of an impulse forces increasing echoes to weaken proportionally. (similarity 0.84)
- Nearby reflective surfaces can load a source and boost its output (similarity 0.84)
- Flat surfaces reflect low-frequency sound specularly but scatter high-frequency sound (similarity 0.84)
- Any change in surface reflectivity, not just bumps, causes sound diffusion (similarity 0.83)
- Every echo implies a ghostly alter-ego hidden behind the reflecting surface (similarity 0.81)
- Low-frequency sound passes through ordinary walls because impedance shifts with frequency (similarity 0.81)
- More diffraction occurs for longer-wavelength, lower-frequency sound (similarity 0.81)
- Early strong versus late weak echoes dictate spectral fluctuation character (similarity 0.81)
- Echoes reshape but never change the total energy in a source spectrum (similarity 0.80)
- Treating a measured reflection can remove it while leaving its audible effect intact (similarity 0.80)
- A single boundary reflecting sound off an omnidirectional source creates frequency-dependent interference lobes (similarity 0.80)
- An echo is partly an original sound from the reflecting material (similarity 0.80)