Matthew van Eerde's web log

Last time I talked about how to calculate a sine sweep mathematically. There's a closed-form solution which is quite elegant but, alas, useless in a practical computer implementation due to the very bug numbers that are being fed to the sin(...) function. A computer implementation will care only about the discrete samples that need to be generated. The integral in the previous post turns out to be counterproductive - we're much more interested in the infinite sequence of φi, and more particularly in their residue mod 2π. Read More...

Suppose you want to generate a continuous sine-sweep from time tstart to time tend. You want the starting frequency to be ωstart, and the ending frequency to be ωend; you want the sweep to be logarithmic, so that octaves are swept out in equal times. Read More...

In a recent post I sung the praises of square waves as a way to get a heckuva lot of power (3 dB more power than a sine wave) into a sample-range-limited signal. It's time to take them down a notch now. A problem with square waves is they're impossible Read More...

A full-scale sine wave has an intensity of -3 dB FS. Read More...

In a previous post I posed several mathematical problems... I'd like to go back and give some answers to them. To reiterate, we take a sine wave period and wrap it around a cylinder... Read More...

Do the first exercise above - print out the original image, cut it out along the lines, and make a cylinder by connecting the short ends together. Rotate the cylinder through various orientations, paying particular attention to the location of the sine wave at all times. Read More...

w(i) = a sin(2πfi / s + ϕ) + c ...you'll burn through 2^32 samples in three hours, six minutes, twenty-five seconds. This is uncomfortably close to reasonable. So I fixed it - almost. Now we use a UINT64 for the sample offset. Well, it turns out that fixing that bug uncovered another bug. Exercise... what is the bug? Read More...