Altering the Perception of Pure Tone Volume by Contrasting Binaural White Noise Frequency

An Illusion by Olivia Joseph, Ella Tubbs, & Omer Eissa If a pure tone is played in one ear, adding noise in that same ear masks the tone. However, playing that same noise in the other ear as well can unmask the pure tone, so that we can distinguish it from the noise. By how much can we alter noise in one ear from the noise in the other ear so that we can still distinguish the tone?

The first audio sample presented is sinusoidal pure tone played only in the left ear. The next audio is the sinusoidal pure tone in the left ear as well as a uniformly distributed white noise sample in the left ear, which masks the pure tone. The next audio is the pure tone and white noise in the left ear, as well as that same white noise in the right ear, which unmasks the pure tone. These three audio samples demonstrate that white noise played over a pure tone makes the pure tone indistinguishable, unless the white noise is present in both ears. The samples will serve as a baseline for our illusion.

The next five audio samples are different experimental conditions, modulating the noise presented in the right ear. We modulated the noise using lowpass filters with decreasing cutoffs, starting with 18375, followed by 11025, 7350, and 3675. These changes allow us to observe the effect on whether or not the way in which we perceive the noise will override the fact that the white noise is different in each ear.

This illusion requires headphones!

Pure tone in left ear

Pure tone in left ear, noise in left ear

Pure tone in left ear, noise in both ears

Condition 1

Condition 2

Condition 3

Condition 4

Condition 5

CITATION: Hirsh, I. J. (1948). The Influence of Interaural Phase on Interaural Summation and Inhibition. The Journal of the Acoustical Society of America.