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Pitch, Time Delay and Frequency Conversion
This page contains two conversion tools: musical pitch to frequency and time delay to comb filtering frequencies.
Musical Pitch to MIDI Key Number and Frequency Conversion
Use this tool to convert musical pitch to MIDI key number and frequency. Select a Pitch from the pull-down menu. It may be useful for filter parameter setting in equalization. [More user guidelines >>]
The default pitch in the pulldown menu is c1, 'central C'. Also try a different Tuning Reference frequency from the pull-down menu on the right (this is omitted from printed frequency tables, that are always based on the standard a1 = 440 Hz).
Time Delay: the Haas Effect and Comb Filtering
Use this tool to find the frequency cancellation (comb filtering) for a given Time Delay.
The Haas 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 time delays are between Td = 5 and 40 milliseconds. A 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 C-2 to b6 (10 octaves, i.e., 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) and the MIDI Pitch (musical notation c1 corresponds to MIDI C3).
Based on the tuning reference frequency (standard a1 = 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 right pull-down menu. For example, the Baroque Period tuning is typically a1 = 415 Hz. This value will now be used as the reference for all frequency calculations.
The lower JavaScript determines the nulling frequencies (comb filtering, 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 following 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 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.