Question 1 Using diagrams list and explain three ways that construction design solutions are used to reduce noise at the source. (20 marks) Noise can be reduced from its source through the use of 3 key ways First way:Soundproof is put in a very closed to separate the source from a building structure. This design have a fully enclosing the source of noise in the housing structure. The mass housing of the source of noise will retract and reflects the source till that time when the noise is fully absorbed by the housing walls. This can be illustrated using the following diagram. Second way:Putting thenoise in a region having higher impedance of acoustic. When the acoustic impedance is higher and the regions are solid barrier as well as the ground regions having bigger masses that can mitigate and absorb the noise spread in the whole structure housing. Examples may include putting the equipment which are noise in the basements then lift the shaft in a position which where it is possible to isolate the noise. This is shown by the diagram below; Page2of9 18528637 – Kameran Al-Razak
Third way: Removing the source of noise from the structure A full removal of the source of noise from the housing structure to help reduce the noise. For this some examples may include putting an electrical substation ancillary to the chief housing structure. The sound generated in the original source shall produce noise to the atmosphere and any giving noise shall be absorbed in the outer skin of the housing. This can be illustrated using the following diagram. Page3of9 18528637 – Kameran Al-Razak
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Question 2 In a diagram explain some of the pathways for flanking sound transmission in building structure. How is this best dealt with? (20 marks) Prototype Flanking Sound Transmission Pathways include the following; Floors – Through Floor and Floor Joist Space Plumbing Chases – Junctures Between the Walls & Floor Slab Above or at the Exterior Wall Juncture Fixtures & Outlets – Light Switches, Telephone Outlets, and Recessed Lighting Fixtures Shared Structural Building Components – Floor Boards, Floor Joists, Continuous Partitions, Continuous Concrete Floors, and Block Walls Ceilings – Above and Through the Ceiling Space Through Windows Ways to help mitigate flanking transmission of sound are staggering items of P/C, fixing / fixtures of electrical as well as the service risers which are back to back having adjoining sole occupancy units. Another key example is caulking all the wall pentation and floor construction to help do away with all pathways for transmission of sound in the structure. Page4of9 18528637 – Kameran Al-Razak
Question 3 Why is structure-borne sound transmission often a problem in older residential apartment blocks? Give an example. (20 marks) Transmission of sound in older block apartment is a key problem since there is a different standards for the construction for given times of construction till now. Majority development in mitigating transmission of sound as well as standard of acoustic which are currently discovered hence older building styles will not be in accordance with the new standards. Current development for the BCA which are in BCA volume 1 and section J set out the current standards in ways of construction to reduce the transmission sound in the housing. Sound transmission examples in older block apartment can be viewed in steel framed structure as good technology for insulation of acoustic where not employed. It is possible for the sound to resonate in the steel subframe of the housing structure hence transmit between several sole occupancy unit in the housing structure. Currently in construction there are ways to mitigate this transmission of sound would constitute composite slab flooring as well as the acoustic underlay to help reflect the sound back for it to be absorbed. For the old structure renovation to comply with the current day acoustic standards is a long process and it is also costly at the same time that owner don’t want to pay for. Page5of9 18528637 – Kameran Al-Razak
Question 4 Describe an example of discontinuous construction being used to reduce sound transmission in buildings. (Hint: Section drawings are essential) (20 marks) The smallest size cavity to reduce the transmission of sound in discontinuous construction is 20 mm . For this construction style every skin of the wall is isolated from each other without any penetration and ties to reduce the amount of transmitted sound between the walls of the structure. Page6of9 18528637 – Kameran Al-Razak
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Question 5 Using diagrams explain some of the principles of auditorium design for live theatre. (20 marks) In Halls sound moves and reaches at the listener directly both from source and indirectly through the sound reflection when it hit the wall and in some cases it can travel through reverberation from the floor, ceiling and the walls or even the combination of the three. If the human ear is presented having reflective sound reaching much later than the direct sound then there will be an automatic response to interpret these just as echoes of the real sound. Nevertheless, if the sound reflected arrives fifty millisecond threshold between direct sound and an echo then the brain will have to interpret these together. The design of the Auditorium will make use of concept of indirect and direct sound to realize earlier reflection to reach the human´s ear but is not done more than fifty millisecond when the real sound is produced this will reduce the late sound reflection which would reach the ear fifty millisecond after the real sound. This is done by the use of dispersive surface as well as reflector in the walls floor as well as arrangement of seating. The reflectors are employed to generate earlier reflection of sound waves and disperse the waves from the key stage to the room ( rear) whilst the absorbent and dispersive surface are used to reduce the amount of indirect sound heard by the human´s ear. Page7of9 18528637 – Kameran Al-Razak