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Conversion tools for Midi key numbers, frequency and time delay calculation

Pitch, Time Delay and Frequency Conversion

This page contains two conversion tools: musical pitch to frequency and time delay to comb filtering frequencies. [More user guidelines >>]

1. Musical Pitch to MIDI Key Number and Frequency Conversion

Use this tool to convert musical pitch (SPN) to MIDI key number, frequency and Helmholtz pitch. Select a Pitch from the pull-down menu. It may be useful for filter parameter setting in equalization.

Convert Musical Pitch to MIDI Key Number and Frequency
Pitch
(SPN):		 MIDI Key
Number:		 MIDI
Pitch:
Tuning Reference
Frequency A4 [Hz]:		 Frequency
f [Hz]:		 Helmholtz
Pitch:

Select a musical pitch from the pull-down menu

The default Pitch in the pulldown menu is C4 = 'Middle C'. Select a different Tuning Reference frequency (most printed frequency tables are based on the standard A4 = 440 Hz).

2. Time Delay: the Precedence / Haas Effect and Comb Filtering

Use this tool to find the frequency cancellation (comb filtering) for a given Time Delay.

Find the Cancelling Frequencies for a given Time Delay
Time Delay
Td [ms]:		 Lowest frequency
cancellation [Hz]:
Higher frequency cancellations [Hz]:
Select a time delay from the pull-down menu

The Haas or precedence effect is used to create depth and focus in an audio mix. This is achieved by mixing the audio signal with a (panned) time-delayed copy. Useful spatial effect time delays are between Td = 5 and 40 milliseconds. For L/R hard panning of mono sources use between Td = 0.1 and 0.7 ms for detailed positioning between left and right speaker. A precedence side effect is the partial or complete cancelling of a set of low frequencies (destructive interference).

Guidelines for the user

The tools on this page may be useful to the audio mixing engineer. The upper JavaScript converts musical pitch into MIDI data and acoustic frequency.

  • Select a pitch from the Musical Pitch pull-down menu. Input values range from C0 to C10 (Scientific Pitch Notation). This implies 10 octaves, beyond the range of the piano keyboard (cathedral organs may have this range). The tool will then determine both the MIDI Key Number (an integer between 12 and 132), the MIDI Pitch (musical notation C4 = MIDI C3) and the corresponding Helmholtz pitch (between C-2 and c7).
  • Based on the tuning reference frequency (standard A4 = 440 Hz), the Frequency of the selected pitch is calculated. These are based on the 12-tone chromatic scale with equal temperament, i.e., fn = f02(n/12), with n = 0, 1, 2, .... In order to reduce numerical errors the frequency of the A in the current octave is determined (multiplication by powers of two) before calculating the chromatic steps.
  • Select a different Tuning Reference from the lower pull-down menu. For example, the Baroque Period tuning is typically A4 = 415 Hz. This value will now be used as the reference for all frequency calculations.

The lower JavaScript determines the nulling frequencies (comb filtering, precedence effect, also called the "Haas effect") for a given time delay.

  • Select a Time Delay in milliseconds from the pull-down menu. The tool will then calculate the cancelling frequencies when the delayed sine wave (i.e., single frequency) audio signal is mixed with the original, non-delayed sine wave. Comb filtering (frequency cancelling) will occur when the original and delayed wave are 1800 out of phase. This yields a series of cancelling frequencies. For a time delay Td in milliseconds, the nulling frequency series is fn = (1+2n) x 1000/(2Td), with n = 0, 1, 2, ...
  • The tool shows the most dominant terms from that series, i.e., the lowest and the next three higher frequencies. For complex audio signals (multiple frequencies) the effect will be dominant at the lowest cancelling frequency. Use this result for setting filter parameters (equalisation) in combination with signal time delays.

Further Reading

  • Bobby Owsinski, The Mixing Engineer's Handbook: Second Edition, Course Technology, Cengage Learning, Boston, MA, 2006 (ISBN 1 59863 251 5).
  • Roey Izhaki, Mixing Audio: Concepts, Practices and Tools, Focal Press, Elsevier, Amsterdam, 2008 (ISBN 978 0 24 52068 1).
  • Michael Boom, Music through MIDI, Microsoft Press, Redmond, WA, 1987 (ISBN 1 55615 026 1).
  • Bob Katz, Mastering Audio: The Art and The Science, Second Edition, Focal Press, Elsevier, Amsterdam, 2007 (ISBN 978 0 240 80837 6).
  • Gardner Read, Music Notation: A Manual of Modern Practice, Victor Gollancz Ltd., London, 1985.
  • Mike Senior, Mixing Secrets for the Small Studio, Focal Press, Burlington, MA, 2011 (ISBN 978-0-240-81580-0).