Sounds below 20 Hz are called infrasound, whereas those above 20,000 Hz are ultrasound. You may have noticed that dogs respond to the sound of a dog whistle which produces sound out of the range of human hearing. Dogs can hear sounds as high as 45,000 Hz, whereas bats and dolphins can hear up to 110,000 Hz sounds. Other animals have hearing ranges different from that of humans. Humans can normally hear frequencies ranging from approximately 20 to 20,000 Hz. It can give us plenty of information-such as pitch, loudness, and direction. A voice becomes louder when air flow from the lungs increases, making the amplitude of the sound pressure wave greater. A voice changes in pitch when the muscles of the larynx relax or tighten, changing the tension on the vocal chords. This vibration escapes the mouth along with puffs of air as sound. As air travels up and past the vocal cords, it causes them to vibrate. These folds open and close rhythmically, creating a pressure buildup. People create sounds by pushing air up through their lungs and through elastic folds in the throat called vocal cords. Power is the rate at which energy is transferred by the wave. In general, the intensity of a wave is the power per unit area carried by the wave. Figure 14.10 shows such a cartoon depiction of a bird loudly expressing its opinion.Ī useful quantity for describing the loudness of sounds is called sound intensity. In cartoons showing a screaming person, the cartoonist often shows an open mouth with a vibrating uvula (the hanging tissue at the back of the mouth) to represent a loud sound coming from the throat. But in a traffic jam filled with honking cars, you may have to shout just so the person next to you can hear Figure 14.9.The loudness of a sound is related to how energetically its source is vibrating. In a quiet forest, you can sometimes hear a single leaf fall to the ground. Sound intensity is defined as the sound power per unit area, whereas amplitude is the distance between the resting position and the crest of a wave. While sound intensity is proportional to amplitude, they are different physical quantities. This eliminates the needįor the clamping function in the above example and provides a smooth attenuationįor any distance from the light source.Students may be confused between amplitude and intensity. The denominator is always larger than the numerator. The light source, you can add a one to the denominator to guarantee that If you don’t want the attenuation to abruptly “kick in” at some distance from One of the equations is more intuitive to you. You get the same results with either equation, but perhaps In the literature you typically see an attenuation equation likeġ0.0 / d written with the proportional constant in the denominator like this,ġ.0 / 0.1*d. Since programmable shaders were introduced, youĬan implement the exact attenuation function that meets your Set the values for c1, c2, and c3 to create a large number of possibleĪttenuation functions. Was used to give programmers control over attenuation. In the original OpenGL lighting model, the equation 1.0/(c1 + c2*d + c3*d^2) However, using differentĪttenuation values for different models in a scene would be uncommon. Variable that is assigned a value at run-time. You could make the constant in your attenuation equation be a uniform If you wanted an attenuation factor that could be changed during run-time, color = attenuation * ( ambient_color + diffuse_color + specular_color ) To_light = u_Light_position - v_Vertex d = length ( to_light ) attenuation = clamp ( 10.0 / d, 0.0, 1.0 ) //.
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