Frequencies of Complex Sounds

1. Frequencies of Complex Sounds • Complex sounds are composed of a fundamental frequency and overtones / harmonics frequencies • Fundamental frequency – lowest frequency; basic resonant frequency; pitch (first harmonic) • Harmonic frequencies – whole number multiples of the fundamental frequency (e.g., 100, 150, 200, 250 Hz…. for a fundamental at 50 Hz) • Overtones – frequencies above the fundamental frequency; may be only harmonics or harmonics plus other frequencies

2. Overtones • Some instruments have overtones not composed of only harmonics • All harmonics are overtones, but not all overtones are harmonics • Overtones give an instrument its characteristic sound

3. Harmonic Differences

4. Fundamental, Harmonics and Overtones Fundamental 2nd Harmonic Non-harmonic Overtones 3rd Harmonic Relative Level (dB) 50 100 150 200 250 Frequency (Hz)

5. Timbre • Timbre – responsible for the distinctive sound of each instrument or sound; it is a very complex and multi-faceted behavior • Oversimplified, timbre is composed of frequency and sound envelope information • Frequency – fundamental, overtones and their relative amplitudes • Sound Envelope – shape of the sound wave (shape and timing of the rise and fall, vibrato, etc.)

6. Timbre - Sound Envelope

7. Frequency Masking • Masking – louder sound hides or masks a lower level sound • Masking increases as the frequency of the two sounds are closer together • Most masking occurs within the critical band • Critical band – 15-20% of the frequencye.g., Critical band for 1000 Hz is 800-1200 Hz (20%)

8. Frequency Masking 1000 Hz tone

9. Reconstructing Missing Fundamentals • If a fundamental or low-order harmonic is missing or very quieter, our brain uses the remaining harmonics to deduce what is missing • Reason we can recognize the low E of a bass even if the monitors cannot reproduce the fundamental of 41 Hz • Has implications when cutting frequencies during mixing

10. Musical Octaves • Human hearing frequency range covers about 10 octaves20 Hz – 20 kHz • The lowest (20 - 40 Hz) and highest (10,240 - 20,480 Hz) octaves have the least amount of useful musical content • Boosting in the lowest octave range can emphasize unwanted rumble and noise, and many monitors cannot accurately reproduce frequencies in this range • Boosting in the upper 1/2 to 2/3 of the highest octave range can emphasize noise and hiss

11. Parametric EQ • A range of frequencies is boosted or cut around a center frequency. • Center frequency– mid-point of the frequency being boosted or cut. Point of maximum boost or cut. • Bandwidth – width or range of frequencies boost or cut. Expressed as frequency bandwidth, octave bandwidth or Q. High Q = narrow bandwidth • Amplitude – amount of boost or cut

12. Parametric EQ Frequency bandwidth shown (3 dB from full boost or cut)

13. Shelving EQ • A sloping curve with a rise or drop in frequency which may taper off at a level • All frequencies beyond the initial boost or cut point are effected • Knee point – frequency where boost or cut occurs. Usually where 3 dB boost or cut occurs (at full boost or cut) • Slope – rate of boost or cut (e.g., 6 dB per octave)

14. Shelving EQ

15. Shelving EQ – High Boost Boosts all frequencies above the knee point

16. Shelving EQ – High Cut Cuts all frequencies above the knee point

17. Shelving EQ – Low Boost Boosts all frequencies below the knee point

18. Shelving EQ – Low Cut Cuts all frequencies below the knee point

19. EQ Filters • Low cut or high pass filter – cuts (removes) all frequencies below the cutoff frequency • High cut or low pass filter – cuts (removes) all frequencies above the cutoff frequency • Bandpass filter – cuts all frequencies above and below the cutoff frequencies. Combines the action of a low and high cut filter

20. EQ Strategies • Start with great sounds and use microphone techniques Banish the thought of “fix it in the mix” • Adjust and refine EQ for the most critical parts of the mix first • Sweep the frequencies to find the good and bad soundsUse a large boost and narrow bandwidth when sweeping • Large (~8-10 dB) boosts or cuts rarely sound good. • Smaller boost with wider bandwidths tends to work better • Cuts with narrow bandwidths avoids loss of important content

21. EQ Strategies • Use subtractive EQ when possible – remove frequencies you do not want (ugly sounds or noise) or to create space for other instruments • Cut some of the fundamental frequency range and boost select overtones to help an instrument cut through a dense or busy mix • Cutting high frequencies can make low frequencies seem louder and vice versa • Cutting the mid-range then raising the overall level often works better than adding highs and lows.

22. EQ Strategies • Use the musical content to determine frequencies to boost or cut • Example: If the fundamental is 220 Hz, there will be substantial content at 440 Hz, 880 Hz, etc.. Boost the harmonics to bring out the track and cut to pull back the track.

23. EQ Strategies • Be careful of making EQ adjustments of isolated (soloed) instruments since you may not be able to tell how it fits in the full mix • Adjust and/or refine the EQ with other instruments in the mix or frequently check the adjustments with the full mix • The order of serial processors does make a difference. Usually compress before EQ, but not a requirement or always “best”

24. Dual Band Boost and Cut – “Mirrored Equalization” • Used for two instruments with similar frequencies • Boost a small frequency range in the first track and cut the same or similar frequency in the second track • Boost a different, but nearby frequency range in the second track and cut the same or similar frequency in the first track • The frequencies, bandwidths and boost/cut levels do not have to be exactly the same

25. Dual Band Boost and Cut

26. Dual Band Boost and Cut