Active questions tagged thd - Signal Processing Stack Exchange most recent 30 from dsp.stackexchange.com 2019-11-19T11:41:25Z https://dsp.stackexchange.com/feeds/tag/thd https://creativecommons.org/licenses/by-sa/4.0/rdf https://dsp.stackexchange.com/q/59983 0 Are Total Harmonic Distortion and Noise (THD+N) and THD correlated in practice? user1420303 https://dsp.stackexchange.com/users/28622 2019-08-07T17:54:11Z 2019-08-07T20:30:52Z <p>I've read about THD and THD+N due to interest in audio quality.</p> <p>Some audio devices (ej. speakers) report %THD or %THD+N. %THD+N is greater than %THD. I've found that sometimes the difference is huge, which makes me think that a significant part of the noise is due to large generation of spurious frequencies (which are not harmonics of the reference input frequency).</p> <p>I think that in similar circumstances non-harmonic frequencies should generate to the hearer a perceived distortion greater than those due to harmonics frequencies (Am I right?). If this is true, the %THD+N must be much more relevant than %THD. In such case %THD can only be relevant for comparing two audio devices if it is positively correlated with %THD+N.</p> <p><strong>Q1</strong> Are %THD+N and %THD correlated in practice in the case of common audio devices (speakers, headphones, amplifiers)? </p> <p><strong>Q2</strong> How important is %THD in the reproduction of the input signal in speakers or headphones?</p> https://dsp.stackexchange.com/q/56318 7 Optimal amplitude of an \$m\$-bit sinusoid Olli Niemitalo https://dsp.stackexchange.com/users/15347 2019-03-29T08:48:27Z 2019-04-14T10:00:48Z <p>A continuous-time sinusoid of zero-to-peak real amplitude <span class="math-container">\$A \le 2^{m-1}-0.5\$</span> (e.g., for <span class="math-container">\$m=16\$</span>, <span class="math-container">\$A \le 32767.5\$</span>) is quantized to <span class="math-container">\$m\$</span>-bit resolution by rounding it to the nearest integer (Fig. 1). What is the optimal amplitude for different <span class="math-container">\$m \le 24\$</span>? </p> <p><a href="https://i.stack.imgur.com/9EWC5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9EWC5.png" alt="enter image description here"></a><br><em>Figure 1. For <span class="math-container">\$m = 4\$</span>, a sinusoid of the maximum allowed amplitude <span class="math-container">\$A = 7.5\$</span> (blue solid line), its quantization (orange dashed line), and the most negative and positive 4-bit two's complement signed integers -8 and 7 (yellow).</em></p> <p>An answer is desired for each of two alternative definitions of optimality:</p> <ol> <li>maximize <a href="https://en.wikipedia.org/wiki/Signal-to-noise_ratio" rel="nofollow noreferrer">signal-to-noise ratio</a> (SNR), where the signal is the original sinusoid and noise is the quantization error, and</li> <li>minimize <a href="https://en.wikipedia.org/wiki/Total_harmonic_distortion" rel="nofollow noreferrer">total harmonic distortion</a> (THD), which is normalized against the amplitude of the fundamental frequency in the Fourier series of the quantized sinusoid.</li> </ol>