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Convert Frequency to Mel Scale

ucnv_hz_to_mel.Rd

Converts frequency values from Hz to the mel scale, a perceptual pitch scale where equal distances sound equally different to human listeners.

Usage

ucnv_hz_to_mel(freq, method = c("htk", "slaney"), as_units = NULL)

Arguments

freq

Numeric vector or units object with frequency values in Hz.

method

Character string specifying the conversion formula to use. Options are:

  • "htk" (default): HTK formula using base-10 logarithm

  • "slaney": Slaney's formula (linear below 1000 Hz)

as_units

Logical. If TRUE, returns a units object with "mel" units.

Value

If as_units = TRUE: a units object with "mel" units. Otherwise, a numeric vector of mel values.

Details

Two formulas are available:

HTK formula (default): $$mel = 2595 \cdot \log_{10}(1 + f/700)$$

This gives exactly 1000 mels at 1000 Hz.

Slaney formula: Linear below 1000 Hz, logarithmic above. Used in some audio processing libraries.

References

(O'Shaughnessy 1987)

Examples

if (FALSE) { # \dontrun{
# 1000 Hz = 1000 mels (approximately)
ucnv_hz_to_mel(1000)

# Vector conversion
ucnv_hz_to_mel(c(100, 500, 1000, 2000, 4000))

# With units
library(units)
freq <- set_units(1000, Hz)
ucnv_hz_to_mel(freq)
} # }