This difference in speeds caused the wave to bend, or be refracted. This is because brick is a solid whose molecules are closer together and can transmit sound more quickly. The part of the wave going through the brick is now going faster than the part in the air. Some of the wave is reflected, but much of it enters the brick.
Imagine sound is traveling through the air and hits the wall of a brick building. The rest enters the new medium and is refracted. Whenever sound hits a new medium, part of it is reflected back. When a wave is reflected, it returns with an angle equal to the one with which it hit. Instead it will bounce off, or be reflected, from the dividing line. If sound hits the new medium with any angle smaller than the critical angle, it will not be able to enter. The greater the difference in speed between the two mediums, the greater the critical angle will be. Because of this, even if the sound hits at the same angle, the angle of refraction will vary for different mediums. The speed of sound is different in every medium. The critical angle depends on the two mediums the sound is coming from and going to. When the wave’s entering angle reaches a certain point, called the critical angle, the refraction is parallel to the dividing line between the mediums. As the angle from the wave to the barrier between the two mediums gets smaller, the angle of refraction also gets closer to the barrier. The angle of refraction depends on the angle that the waves has when it enters the new medium. Refraction is also discussed more in the following page. The difference in speeds causes the wave to bend. Because of the angle, part of the wave enters the new medium first and changes speed.
Refraction is caused by sound entering the new medium at an angle.
This change in angle of direction is called refraction. When sound changes mediums, or enters a different material, it is bent from its original direction. Sound waves travel outward in straight lines from their source until something interferes with their path. Remember that sound travels faster in some materials than others. They want every member of the audience to hear loud, clear sounds. The shape of the building or stage and the materials used to build it are chosen based on interference patterns. Engineers who design theaters or auditoriums must take into account sound wave interference. Dead spots occur when the compressions of one wave line up with the rarefactions from another wave and cancel each other. Waves can interfere so destructively with one another that they produce dead spots, or places where no sound at all can be heard. As a result, we hear pulses or beats in the sound. When waves are interfering with each other destructively, the sound is louder in some places and softer in others. When the compressions and rarefactions are out of phase, their interaction creates a wave with a dampened or lower intensity. This type of interference is known as constructive. If the compressions and the rarefactions of the two waves line up, they strengthen each other and create a wave with a higher intensity. The new wave is the sum of all the different waves. When two or more sound waves from different sources are present at the same time, they interact with each other to produce a new wave.