Let’s start by listening to the original 100 Hz sine wave with a level of -10 dB FS without any other additional components. If you hear any distortion or noise, then this is a problem in your playback system (unless your system is so good that you can hear the quantisation error caused by the fact that I didn’t dither the signal).<\/p>\n
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<\/a><\/p>\n<\/div>\nVersion 2: Wide-band noise<\/strong><\/div>\nNow let’s add noise. I’ve added noise with a white spectrum and a level such that a THD+N measurement will tell us that we have 10% THD+N (relative to the level of the 100 Hz sine tone signal). In other words, I have a sine wave with a level of -10 dB FS and I have added white noise with a long-term RMS level of \u00a0-30 dB FS.<\/p>\n
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<\/a><\/div>\n<\/div>\n\u00a0It should be pretty obvious, even with poor playback equipment, that I have added noise to the 100 Hz tone. This should not be surprising, since a 10% THD+N is pretty bad.<\/div>\n<\/div>\nVersion 3: 2nd harmonic<\/strong><\/div>\n<\/div>\nFor this version, I’ll add a 200 Hz sine tone to the 100 Hz tone. The fundamental (100 Hz) has a level of -10 dB FS. The level of its second harmonic (200 Hz) is -30 dB FS. This means that, again, I get a THD+N value of 10%.<\/div>\n<\/div>\n<\/div> \n\n\n- \n\n
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<\/a><\/p>\n<\/div>\nVersion 4: 3rd harmonic<\/strong><\/div>\n<\/div>\nFor this version, I’ll add a 300 Hz sine tone to the 100 Hz tone. The fundamental (100 Hz) has a level of -10 dB FS. The level of its third harmonic (300 Hz) is -30 dB FS. This means that, again, I get a THD+N value of 10%.<\/div>\n<\/div>\n<\/div> \n\n\n- \n\n
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<\/a><\/div>\n<\/div>\nVersion 5: 2nd to 5th harmonics<\/strong><\/div>\n<\/div>\nFor this version, I’ll add a four additional sine tones to the 100 Hz tone. The fundamental (100 Hz) has a level of -10 dB FS. I have added tones at 200 Hz, 300 Hz, 400 Hz and 500 Hz (the 2nd through to the 5th harmonics, inclusive) with a spectral pattern where each successive tone is half the amplitude of the previous. In other words, 500 Hz is half the amplitude of 400 Hz which, in turn, is half the amplitude of the 300 Hz tone, which is half the amplitude of the 200 Hz tone.<\/div>\n<\/div>\nI have adjusted the overall level of the harmonics so that we get a THD+N value of 10%. In other words, the RMS level of the signal comprised of the 200 Hz to 500 Hz sine tones (inclusive) is -30 dB FS.<\/div>\n<\/div>\n<\/div> \n\n\n- \n\n
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<\/a><\/div>\n<\/div>\nVersion 6: 5 kHz<\/strong><\/div>\n<\/div>\nFor this version, I’ll add a 5 kHz sine tone to the 100 Hz tone. The fundamental (100 Hz) has a level of -10 dB FS. The level of the 5 kHz tone is -30 dB FS. This means that, again, I get a THD+N value of 10%.<\/div>\n<\/div>\n<\/div> \n - \n
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