1.1 Introduction to acoustics

Acoustics is the science of sound: how it is produced, how it travels through air and materials, and how it is received and perceived by people. In interior design, acoustics is concerned with making spaces sound right for their purpose, so that speech is clear in classrooms and meeting rooms, music sounds rich in halls and churches, conversations stay private in clinics and offices, and unwanted noise from outside or neighbouring rooms is kept out. Acoustic quality is achieved through the shape and size of spaces, the choice and placement of finishes, the construction of walls, floors, ceilings, doors and windows, and the layout of activities. Example: a newly fitted open-plan office for an insurance company was attractive but so echoey that staff could not concentrate, until the designer added acoustic ceiling panels, fabric wall panels and carpet tiles, transforming the working environment.

1.1.1 Branches of acoustics

Acoustics is a broad field with several branches, each focusing on a different aspect of sound. Interior designers work mainly with architectural and room acoustics, but they meet ideas from other branches too. Example: when designing a recording studio for a community radio station, the interior designer works alongside specialists in room acoustics, building acoustics and electroacoustics.

1.1.2 Development of architectural acoustics

People have shaped spaces for sound for thousands of years, but architectural acoustics became a science only in the last century. Understanding its development helps designers appreciate why modern acoustic methods work. Example: designers of a cathedral's renovation study how the original stone vaults and timber pews shaped the sound before adding modern acoustic treatment.

1.1.3 Scope of interior acoustics

Interior acoustics covers all the ways sound is managed inside buildings. It applies to every type of space, although the goals differ from one space to another. Example: in a primary school, the designer focuses on speech clarity in classrooms, sound insulation between classrooms and the noise level in the dining hall.

Areas covered by interior acoustics

• Room sound quality: Shaping how sound behaves inside a room so speech and music are clear and pleasant.
• Sound insulation: Preventing sound passing between rooms and from outside through walls, floors, ceilings, doors and windows.
• Noise control: Reducing noise from equipment, services, traffic and people.
• Speech privacy: Keeping conversations confidential in clinics, offices, banks and legal spaces.
• Impact sound control: Reducing sounds of footsteps and dropped objects through floors.
• Sound system coordination: Working with sound engineers on loudspeaker positions and equipment rooms.
• Acoustic comfort: Creating spaces where people feel calm and can concentrate.

1.1.4 The interior designer's role in acoustics

Interior designers make many decisions that strongly affect acoustics, such as the layout of rooms, the choice of finishes and furniture, and the detailing of partitions and ceilings. On large or sensitive projects they work with acoustic consultants, but on most projects they are responsible for achieving acceptable acoustic conditions themselves. Example: a designer for a law firm places meeting rooms away from the open office, specifies full-height partitions with acoustic seals on doors and adds soft furnishings to reduce echo.

Responsibilities

• Planning layouts: Separate noisy and quiet activities, such as placing plant rooms away from bedrooms.
• Selecting finishes: Choose a balance of hard and sound-absorbing surfaces to suit each space.
• Specifying partitions and ceilings: Choose constructions with suitable sound insulation.
• Detailing junctions: Seal gaps around doors, partitions and services where sound can leak.
• Choosing furniture and soft furnishings: Use upholstery, curtains and rugs that help control sound.
• Coordinating with specialists: Work with acoustic consultants, engineers and sound system suppliers.
• Complying with regulations: Meet legal noise limits and building requirements.

Professionals involved in acoustic design

1.1.5 Instruments used in acoustic assessment

Acoustic conditions are measured with instruments so that problems can be identified and improvements checked. Interior designers should recognise these instruments and understand their use, even if specialists operate them. Example: before refurbishing a call centre, a consultant measures background noise and echo so that the improvement after treatment can be demonstrated to the client.

1.1.6 Regulations and standards on noise in Kenya

Noise in Kenya is controlled by law, and interior designs must help buildings and their users comply. Designers should know the main regulations and standards that apply to their projects. Example: a designer creating an entertainment lounge in a mixed-use building specifies sound-insulated walls and a lobby at the entrance so that music does not exceed permitted levels in neighbouring apartments.

Laws and standards

• Environmental Management and Co-ordination Act (EMCA): The main environmental law, under which noise pollution is controlled.
• Noise and Excessive Vibration Pollution Control Regulations, 2009: Set maximum permitted noise levels for different zones and times of day, and require permits for activities producing excessive noise.
• National Environment Management Authority (NEMA): Enforces noise regulations and issues licences and permits.
• County by-laws: Counties control noise from entertainment venues, businesses and events within their areas.
• Occupational Safety and Health Act, 2007: Protects workers from harmful noise exposure in workplaces.
• Building and international standards: Kenyan building regulations and international acoustic standards give guidance on sound insulation and room acoustics.