Final answer:
3D sound and surround-sound are indeed different, 3D sound simulates a three-dimensional audio environment, while surround-sound provides multi-channel audio at ear level. Holograms are true three-dimensional images viewable from various angles, unlike 3-D movies. Waves can superimpose with different frequencies, and sound levels are affected by constructive and destructive interference.
Step-by-step explanation:
The statement 3D sound is different from surround-sound is true. 3D sound, often referred to as spatial sound, is designed to create the illusion that sound sources exist within a three-dimensional environment around the listener, which can include the perception of height, depth, and distance. This is different from traditional surround-sound systems, which mainly focus on providing multiple audio channels around the listener, generally at ear level, without necessarily simulating height or exact positioning.
Holograms are true three-dimensional images because they record and display all the light information from an object, including phase and amplitude, which creates a fully dimensional image viewable from different angles. In contrast, 3-D movies use stereoscopic techniques that give an illusion of depth, as two slightly different images are presented to each eye to simulate three-dimensionality, but they do not offer a true full-range view as holograms do.
Additionally, it is true that waves can superimpose if their frequencies are different. This phenomenon is related to the principle of wave interference, which is a process where two waves meet while traveling along the same medium. Similarly, it is true that the two types of interference are constructive and destructive interferences. Constructive interference occurs where wave amplitudes reinforce each other, leading to a larger amplitude, while destructive interference leads to a reduction in amplitude.
The statement that sound is louder in parts of a room where constructive interference occurs and softer where destructive interference occurs is also true. This is because when waves meet in phase, they amplify the sound (constructive), and when they meet out of phase, they cancel each other out to some extent (destructive).
Lastly, the statement that the Doppler effect occurs only when the sound source is moving is false. The Doppler effect can occur if either the source or the observer is moving relative to the medium through which the waves are transmitted.