Listening to pH

Abstract

We developed a simple device to teach the concept of pH to visually impaired people through an experimental approach. An interface between a glass electrode and an open-source electronics platform based on easy-to-use hardware and software (Arduino Uno) was designed using an operational amplifier of ultralow input current. A headphone connected to digital output from Arduino Uno was employed to convert the electrical signals from pH to sound frequency. Using an audio file that emits sound frequencies, visually impaired students were trained to associate specific frequencies with pH values. There is a direct relationship between the logarithm of sound frequency from a given musical note and a pH value, which can be used to train students with low vision who would otherwise have difficulty observing pH values from visual indications. Sound frequency signals of 131–659 Hz that correspond to the piano musical scale of C3, which is one octave below middle C (small octave or the “Do” note in solfège), to E5, one octave above middle E (two-lined octave or “Mi” note in solfège), were used to obtain sounds for the pH scale. Each musical note from these scales corresponded to one pH value with precision of 0.5 unit. This proposed method can be easily implemented in a laboratory with a relatively low cost.