Determine the frequency of the sound wave. If you are given a visual graph of the sound wave, you can calculate the frequency of the wave by counting the number of complete wave cycles that occur in the given time increment and multiplying that number by the inverse of the percentage of one second the given time increment is equivalent to. Like all waves, the sound wave contains a series of peaks and troughs. The distance from peak to peak or trough to trough is the equivalent of one complete cycle of the wave.
Compare the frequency of the wave to standard pitch references. For example, the 'A' above middle 'C' on the keyboard occurs when a sound wave is traveling at 440 Hz. Like the 12-note scale, sound frequencies also contain inherent relationships. The 'A' and octave above 440 Hz occurs when a sound wave is traveling twice the speed of the original pitch, thus 880 Hz. Consult the chart listed as the first reference below to assign your calculated wave frequency to a pitch.
"Play" the frequency by producing the calculated pitch on your instrument of choice. Using the method detailed above, you can easily translate a variety of sound frequencies into pitches. Keep in mind that pitches are often labeled with their note name and number detailing their octave placement on the keyboard. "Middle C" is written as C4. Any notes above C4 that remain below C5 are assigned the number 4. Use these references to translate pitch names into actual locations on the keyboard.