Line sources need listeners in the near field to keep their −3 dB falloff

Evidence

Practical line sources have finite lengths, so the critical issue becomes one of keeping listeners within the near field of the line, where the desirable −3 dB/double distance propagation loss relationship holds, and out of the far field where even line sources revert to −6 dB/double-distance. Obviously, the distance at which the near-/far-field transition occurs is a function of frequency and the length of the line. So, interestingly enough, for conventional loudspeakers we may wish to be in the acoustical far field, but for true line sources we need to be in the acoustical near field to appreciate the benefits. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1278

Categorization

Category: Causal Relationships

• XREF: Ties to the earlier discussion of the far-field measurement distance conventions for point-source loudspeakers.

Related

• Near-field versus far-field acoustics change which partials a listener hears (similarity 0.80)
• Near-field sound measurement is unreliable when multiple source parts radiate simultaneously (similarity 0.80)
• Full-height line sources halve the off-center damage to envelopment (similarity 0.79)
• Influential early analysis found truncated line sources have little to recommend them (similarity 0.78)

Broader Connections

• Adjacent compression and rarefaction regions can short-circuit and kill radiated sound #complicates (0.85) — Eric J. Heller, Why You Hear What You Hear- An…, 669