Linear prediction order scales with sample rate to capture speech formants.

Evidence

When the LP order is increased, the LP spectrum resolution improves. The LP order 8 (Figure 3.12e) already yields a fairly good approximation, and orders 10–12 are considered high enough for speech with a sample rate of 8 kHz. More generally, an order equal to the sample rate in kHz plus two is recommended for speech, since it is enough to represent speech formants and the general shape of the spectrum. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 438

Categorization

• SEED: Good rule-of-thumb detail for a practical article on speech analysis or audio DSP tooling.
• corroborated: 2 independent passages support this claim — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 438