Final answer:
The special features to consider when choosing materials for a soundproof room include sound absorption and sound transmission class, which are critical for minimizing echo and blocking sound. Acoustic impedance also affects sound reflection at material boundaries, with differences leading to more reflections. Understanding sound interference is also beneficial for managing the loudness within the room.the correct answer is b) Sound absorption and sound transmission class
Step-by-step explanation:
When choosing the materials that make up the walls of a soundproof room, the key features to consider are sound absorption and sound transmission class (STC). Sound absorption is the ability of a material to absorb sound energy rather than reflecting it, which helps to minimize the echo and reverberation within the room. Materials with high sound absorption rates can significantly reduce the amount of sound that is reflected back into the room.
Sound Transmission Class is a rating of how well a partition attenuates airborne sound. The higher the STC rating, the more effective the material is at blocking sound from passing through it. When considering the physics of the sound, one must account for acoustic impedance, which is a measure of how much resistance a medium gives to the transmission of sound waves. Differences in acoustic impedance at the boundaries between two different media can result in the reflection of sound waves, hence it is crucial to choose materials that ensure a minimal difference in impedance to reduce these reflections.
Finally, it's important to understand that sound behaviors such as constructive and destructive interference can affect the loudness of sound within the room. Constructive interference occurs when sound waves meet and combine to create a wave with a higher amplitude, leading to louder sound, while destructive interference happens when waves combine to form a wave with lower amplitude, resulting in softer sound.