Sounds of frequencies less than about _____ cannot be detected by the human ear.

The correct answer is 20 Hz.

Key Points

• The human ear is capable of detecting sound frequencies within the range of approximately 20 Hz to 20,000 Hz (20 kHz).
• Frequencies below 20 Hz are known as infrasound, which are not audible to humans under normal circumstances.
• Sounds in the infrasound range (below 20 Hz) can sometimes be perceived indirectly as vibrations, particularly at higher intensities.
• The lower limit of human hearing varies slightly among individuals, but 20 Hz is widely accepted as the standard threshold.
• Animals such as elephants and whales can detect infrasound frequencies, which are useful for communication over long distances.

Additional Information

• Hertz (Hz): It is the unit of frequency in the International System of Units (SI), representing one cycle per second.
• Infrasound: Sounds with frequencies below 20 Hz, often produced by natural phenomena like earthquakes, volcanic eruptions, and ocean waves.
• Ultrasound: Sounds with frequencies above 20,000 Hz, commonly used in medical imaging (e.g., ultrasound scans) and industrial applications.
• Hearing sensitivity: Human hearing is most sensitive to frequencies between 2,000 Hz and 5,000 Hz, where speech sounds predominantly occur.
• Hearing range variations: Factors like age, health, and environmental noise exposure can affect an individual's hearing range, often reducing the upper limit as they age.