The ability to perceive sound is critical for the survival of most species on Earth, including humans. The ability to assess the environment through hearing evolved in a variety of ways in the animal kingdom, and high-functioning animals such as humans adapted the sense of sound as a means to communicate.Know More
Sound is created when mechanical energy travels through an elastic medium, such as air. These waves of energy travel into the ear, where the brain interprets them as sound, alerting the listener to potential predators, environmental threats, food, water or peers. Hearing the sound of an approaching tiger, an impending waterfall or a potential meal increased the chances of early human survival. The development of language increased human reliance on hearing as humans learned to express more complex ideas through sound.
In modern times, hearing traffic or the din of a restaurant alerts people to the same dangers and attractions. Humans and animals began using vocal communication long before the development of language, alerting one another to threats, food and mates. The great apes, such as chimpanzees and gorillas, provide excellent examples of pre-language vocal communication. When observed in groups, they can be seen communicating with one another through a variety of sounds and gestures.Learn more about Optics & Waves
The frequency of a sound wave determines what people hear as pitch. A higher frequency has a higher pitch, and a lower frequency is heard as a lower pitch. The frequencies that humans can hear range from 20 to 20,000 Hertz.Full Answer >
In optics, the critical angle is the greatest angle at which a light ray, travelling in one transparent medium, can strike the boundary between that medium and a second less dense medium without being totally reflected within the denser medium.Full Answer >
The speed of sound is dependent on the medium through which it is traveling. Under typical conditions, at sea level, sound travels 1,225 kilometers per hour, or 340.29 meters per second.Full Answer >
The dreams-for-survival theory states that dreams have helped humans evolutionarily by simulating threats, thus preparing people to fight for survival. It is also called the threat simulation theory.Full Answer >