SoundScope

A real-time audio spectrum analyser for iPhone and iPad.

SoundScope draws the sound around you as a scrolling spectrogram: time running across the screen, frequency up it, and colour for how loud each frequency is. A live plot of the current spectrum sits alongside. Touch the picture anywhere and it names the frequency under your finger and the nearest musical note, with the error in cents.

Point it at a guitar you’re tuning, a bearing that has started to whine, the hum of a room, or a bird.

The frequency axis is yours

Most analysers choose a vertical scale and leave you with it. This one gives you both, and the range as well.

• Linear or logarithmic. Logarithmic gives every octave the same room on screen, which is roughly how hearing works. Linear gives every hertz the same room, which is what you want when you are chasing a harmonic series or hunting one fixed-frequency whine.
• Your own minimum and maximum, in either mode. Type them in, or start from a preset: full range, voice, music, bass.

Changing the axis re-lays the whole display rather than relabelling it. The spectrogram, the level plot, the gradations, and the readout all move together, so a peak always sits beside the number that names it.

The rest of the controls

• Level range, the loudness window that the colours are spread across. Raise the floor to cut room noise; lower the ceiling to bring out quiet detail.
• FFT size from 512 to 8192, and a choice of window function. Larger sizes separate two close tones; smaller ones react faster. The app tells you the resulting bin width in hertz and window length in milliseconds as you change it.
• Speed, in spectrogram columns per second, which sets the analysis hop. It is a real time-resolution control, not a scroll animation.
• Four colour maps, and note names with middle C as either C4 or C3.
• Landscape by default, since a spectrogram wants width. Portrait and free rotation are a tap away.

Privacy

Audio is analysed as it arrives and discarded. Nothing is recorded, saved, or transmitted, and the app has no networking code at all. The full privacy policy has the details.

Getting it

SoundScope is in TestFlight by invitation while it settles down. If you’d like a build, email me at email@davidfwatson.com.