http://sound.westhost.com/abx-tester.htm
of dithering and noise-shaping to digital audio.
http://margo.student.utwente.nl/el/misc/n_shape.zip
http://www.geocities.com/SoHo/2022/auditrig.gif
It sweeps the drive frequency slightly to produce a very annoying 120db sound when measured at 12 inches.
http://www.imagineeringezine.com/PDF-FILES/beeper4.pdf
An off-the-shelf piezoelectric beeping device is driven at resonance to insure maximum efficiency.
http://www.imagineeringezine.com/PDF-FILES/beeper3.pdf
from -10dBV unbalanced to 150 ohm balanced microphone level (-45dBu) signal and from +4dBu balanced signal to -10dBV unbalanced signal
http://www.jensen-transformers.com/as/as081.pdf
from +4dBu balanced output to -10dbV consumer equipment input
http://www.jensen-transformers.com/as/as012.pdf
http://www.wenzel.com/pdffiles/phasesft.pdf