1. Relating to sounds or the sense of hearing: The acoustical characteristics of the apartment in the noisy city helped the inhabitants to enjoy a quieter lifestyle.
2. Concerning sounds that are made by musical instruments and voices: Margaret loves to listen to acoustical folk music.

Greek: hearing, listening, of or for hearing.

A unit about hearing or listening words also includes two self-scoring quizzes to challenge your knowledge.

The top of a room that is covered with, or constructed with, material that is designed to control or to absorb sounds: It was necessary for the gym, where the students played basketball, to have an acoustical ceiling because all of the noise caused by the students or players and the spectators was irritating everyone.

A panel or similar device that is suspended from an auditorium ceiling: An acoustical cloud was positioned above the orchestra so it could reflect the musical sounds better for the audience.

One music hall had several acoustical clouds suspended from the ceiling, however the architect forgot to take into consideration that heat from the audience and the performers could send the acoustical clouds spinning around over the heads of the audience and therefore the architect had to come up with a better solution.

The practical applications of the science of sounds: Acoustical engineering deals with the control of sounds and vibrations, however it is concerned not just with audible sounds, but also with phenomena that range from barely measurable magnitudes on up to levels capable of causing severe damage.

The normal areas of acoustical engineering include, among others: architectural and musical acoustics, noise and vibration control, underwater acoustics, ultrasonics, communication engineering, shock and vibration engineering, and instrumentation engineering.

• Architectural and musical acoustics or environments involving sounds.
• Noise and vibration control or keeping sounds within acceptable limits.
• Underwater acoustics or sonar engineering oceans.
• Ultrasonics or ultra-high-frequency sounds and vibrations.
• Communication engineering or the transmissions of spoken information.
• Shock and vibration engineering is a part of mechanical and structural engineering.
• Instrumentation engineering relates to all of the preceding issues, such as the design and applications of sensors for sounds and vibrations, of sounds and vibration generators, of recording systems, and of data analysis equipment.

Any fabric or composition of material that is designed to reduce sounds or to absorb unwanted noises: The architect ordered acoustical material for the ceiling of the room from a reputable dealer who specialized in sound systems.

Any of various military techniques that involve the use of sound-detection devices to obtain information for intelligence purposes: The members of the intelligence team of the national army used special equipment for acoustical surveillances in order to detect underground tunnels and shafts which the revolutionaries might have been using.