Version 2.2 with 44kHz sampling rate!
HASA is a handheld audio frequency spectrum analyzer for Windows Mobile devices. Frequency components of sounds picked up by the built-in microphone are shown and analyzed in real-time. The frequency decomposition can be shown as a standard plot of dB vs. Hz or as a "cascade" plot, showing its time evolution. The standard plot can be shown as a line or ISO bar chart. For checking purposes, an artificial White Noise signal can be applied to the Fourier Transform (yielding a flat frequency response). The user may choose to average the frequency response data over an extended period of time, and exclude a region of the measured time data in order to remove any observed transient anomalies that may appear. Clipping at the microphone is indicated on the HASA display, as are the real-time measured samples and their frequency spectrum.

The measured spectrum can be A-Weighted, and can be stored as a file in the device. Stored spectra can be loaded at run time, and subtracted from the current spectra in order to correct the data. A built-in oscillator generates pure tones across the full audio spectrum, or can generate White Noise for frequency response measurements etc.. Another included feature is note detection, where the equivalent piano note on the equal-tempered scale is detected from the measured spectrum. This in principle allows a quick determination of whether a musical instrument is badly off tune or not...
A full installation and user guide is included.
Possible Applications:

• Measuring sound levels in a car, plane, room, rock concert etc..
• Measuring the frequency response of audio equipment, e.g. loudspeakers
• Measuring frequencies and levels of noise from equipment.
• Measuring fidelity of home or car audio systems (e.g. using the built-in White noise generator, or a test CD).
• Measuring frequency of an opera singer's top A!

1. Version 1.1 handles Audio interrupts more reliably, and adds automatic time domain plot scaling.
2. Version 1.2 offers a new feature of a musical note identifier (equal tempered scale). This feature shows the frequency of the loudest detected sound as the corresponding note on the piano scale.
3. Version 1.3 features improved stop/start stability, and a simple pure tone oscillator that is activated by tap/hold on the frequency plot.
4. Version 1.4 includes a new feature that allows the optional display of the absolute deciBel (dB) sound level.
5. Version 1.5 increases the number of audio record buffers, so avoiding starvation of the audio system. This improves the fidelity of the spectrum especially on iPAQ devices. Also, improved graphics handling in this version has reduced display flicker.
6. Version 1.6 optionally shows the peak FFT values as a decaying plot superimposed on the latest FFT. This feature is useful for observing the envelope of the peak frequency response over the last few seconds.
7. Version 2.0 new features include Save/Load of frequency spectra, subtraction of loaded spectrum, A-weighting in 8 octave bands, a logarithmic sum giving the overall noise level, and a White Noise generator.
8. Version 2.1 adds pulse-mode frequency response analysis, and ISO-centred bad graph display.
9. Version 2.2 allows the dB scale limits to be set, and increases the sampling rate on the PocketPC 2002 devices to 44kHz. This allows audio frequencies up to 22kHz to be measured. There are also some code optimizations which improve performance, particularly for the iPAQ devices.