Logarithmically swept sines measure distortion and match human auditory frequency scaling
Evidence
Logarithmically swept sines can also be used, which allow for the simultaneous measurements of the distortion components (Farina, 2000). Here, the excitation signal x0(t) = a sin[ω(t)t], where the value of ω(t) is logarithmically changed from the lowest to the highest frequency to be measured. This means that a change in the frequency of the sweep is slow at first, and it accelerates exponentially. Typically, the temporal length of the sequence varies from between a few seconds to a minute. In principle, the longer the sweep, the better the signal-to-noise ratio obtained. However, the non-linear properties of the system limit the length of the sequences that can be used; the impulse responses may show, for example, time-smearing of the impulses if the sweeps used are too long. The swept-sine method also allows free control over the distribution of frequencies in the measurement, which is often desired since the frequency scale of human hearing is more logarithmic than linear. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 493
Categorization
Category: Causal Relationships
- XREF: The logarithmic frequency matching of the sweep to auditory perception echoes the reader’s deep-listening and soundscape work on how hearing scales frequencies.
- ADDENDUM: Supports the trees article’s infrastructure framing by analogy: engineered excitation signals as infrastructure for accurate measurement, matching how engineered acoustic systems underpin reliable capture.