Question

When a tuning fork is struck I hear two tones. From a distance I can hear a high octave frequency of the pitch of the tuning fork. Though, if I listen to it closely (closer to my ears), I also hear a lower octave frequency of the pitch of the tuning fork. I want to clarify that what I’m hearing is correct.

Also, is there something about "pure tones" that produces this effect, and if so what are the harmonics of a pure tone/tuning fork. Just from brief reading on the topic, I’ve seen it said that tuning forks overtone(s) (i’m assuming there is only one overtone) ring out quickly. Then why am I hearing a high octave version of the forks pitch and a low octave version of the forks pitch until it rings out?

Answer 1

A tuning fork produces a fundamental frequency and overtones, which contribute to what is heard. The lower overtones might become more noticeable at close range due to environmental acoustics or ear sensitivity, though tuning forks are designed to emit a pure tone.

Step-by-step explanation:

When you hear a tuning fork produces different tones, you're experiencing its fundamental frequency and harmonics or overtones. The fundamental frequency is the lowest and usually most powerful tone, while overtones are higher frequencies that occur at integer multiples of the fundamental frequency. When near the tuning fork, the lower frequencies or overtones might be more noticeable, including potentially a lower octave, which could be due to the acoustic properties of the environment or your proximity affecting how you perceive the sound.

Harmonics are a crucial component of the sound of musical instruments, contributing to their timbre or character, and result from the natural resonances of the instrument's body and the air within it. A resonance within a tube, for example, amplifies certain frequencies. A tube closed at one end will favor odd harmonics, while a tube open at both ends also supports even harmonics, making its tone richer.

Hearing different octaves from a tuning fork isn't typical, as tuning forks are designed to produce a pure tone, mainly the fundamental frequency. However, there could be various explanations, such as acoustic effects within the listener's vicinity, nonlinearities in the listener's ear at high sound pressure levels, or misinterpretation of the sounds due to complex interactions of the sound waves in the surrounding environment and within the ear itself.