Audio Spectrum Analyzer is a remarkable app by Black Cat Systems that transforms your iPhone into a professional-grade audio spectrum analyzer. With the ability to display frequencies up to 20 kHz, this app provides a comprehensive analysis of audio signals.

This app offers a range of features that allow you to customize your analysis. You have control over the displayed frequency span, as well as the FFT size, which can range from 1024 tobins. Additionally, you can choose a logarithmic display of the 10 Hz to 20 kHz frequency range, providing a clear visualization of the entire spectrum.

To enhance the accuracy of your analysis, you can apply filtering (averaging) to the spectrum, which smooths out variations. The app also offers the option to turn on Peak Hold, making it easier to observe transient events, with the ability to adjust the decay rate.

The user interface is intuitive and user-friendly. Adjusting the brightness of the spectrum or the graticule grid overlay is as simple as swiping with two fingers. Moreover, tapping three times with two fingers allows you to conveniently save a screenshot to your Photos.

Audio Spectrum Analyzer offers a variety of window functions for analysis, including rectangular, Hanning, Hamming, Tukey, Cosine, Lanczos, and Blackman. This allows you to select the most appropriate window function for your analysis needs.

Overall, Audio Spectrum Analyzer is a powerful tool for audio analysis on your iPhone. Whether you're a sound engineer, musician, or simply curious about the frequencies in your audio, this app provides accurate and customizable analysis in the palm of your hand.