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Convert Frequency to Semitones

ucnv_hz_to_semitone.Rd

Converts frequency values to semitones relative to a reference frequency. In equal temperament, each semitone represents a frequency ratio of 2^(1/12).

Usage

ucnv_hz_to_semitone(
  freq,
  ref_freq = NULL,
  ref_source = c("A4", "UEP83", "Praat"),
  as_units = NULL
)

Arguments

freq

Numeric vector or units object with frequency values in Hz.

ref_freq

Reference frequency in Hz. Default is NULL, which uses the reference determined by ref_source. Can also be a units object. If specified, overrides ref_source.

ref_source

Character string specifying the reference standard. Options are:

  • "UEP83": UEP 1983 standard (110 Hz = A2/A₁ in Helmholtz notation)

  • "Praat": Praat convention (100 Hz arbitrary reference)

  • "A4" (default): Concert pitch A4 = 440 Hz

Ignored if ref_freq is explicitly specified.

as_units

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

Value

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

Details

The conversion formula is: $$ST = 12 \cdot \log_2(f / f_{ref})$$

where f is the frequency and f_ref is the reference frequency.

Reference Standards:

  • UEP 1983 (Schutte & Seidner): Uses 110 Hz (A2, or A₁ in Helmholtz notation) as the reference for voice range profiles (phonetograms). This standard is commonly used in clinical phoniatrics and voice assessment.

  • Praat: Uses 100 Hz as an arbitrary reference frequency for semitone-based pitch analysis. This provides a convenient round number for relative pitch measurements in speech analysis.

  • A4 (default): Uses 440 Hz (A4, concert pitch) as reference, following standard musical tuning conventions.

This gives the number of semitones above (positive) or below (negative) the reference frequency.

References

(Schutte and Seidner 1983)

Examples

if (FALSE) { # \dontrun{
# Using different reference standards
ucnv_hz_to_semitone(220, ref_source = "UEP83")   # 12 ST above 110 Hz
ucnv_hz_to_semitone(200, ref_source = "Praat")   # 12 ST above 100 Hz
ucnv_hz_to_semitone(880, ref_source = "A4")      # 12 ST above 440 Hz

# Explicit reference frequency (overrides ref_source)
ucnv_hz_to_semitone(880, ref_freq = 440)

# Musical notes relative to A4
ucnv_hz_to_semitone(c(440, 494, 523.25, 587.33, 659.25, 698.46, 783.99, 880))

# With units
library(units)
freq <- set_units(880, Hz)
ucnv_hz_to_semitone(freq, ref_source = "A4")
} # }