Acoustic terms - Glossary for sound insulation and sound absorption

Understanding acoustic concepts is crucial when it comes to improving sound environments through sound insulation and sound absorption. Whether you are working to reduce noise in an office, improve the acoustics in a home theater, or optimize the sound environment in a studio, it is important to know the basic terms used in acoustics. Sound behaves differently depending on the environment and the materials it encounters, and in order to manage sound effectively, a basic understanding of how it works is required.

Sound absorption is about reducing reverberation by trapping sound waves in highly porous materials, while sound insulation aims to block sound from spreading between different spaces. An important factor in this context is the absorption coefficient, which measures how effectively a material can absorb sound. A material with a coefficient of 1 absorbs all sound, while one with a coefficient close to 0 reflects most of it.

Another basic concept is the decibel (dB), which is used to measure sound levels. Higher decibel values mean louder sounds, and each increase of 10 dB is perceived as a doubling of the sound volume. This is particularly relevant in sound insulation, where the goal is to reduce sound levels between different spaces. To achieve effective sound insulation, materials with a high STC (Sound Transmission Class) are often used, which indicates how well a wall, floor, or ceiling blocks sound.

In rooms where sound quality is important, such as theaters or conference rooms, reverberation time (RT60) is a critical factor. It measures how long it takes for the sound to decrease by 60 dB after the sound source has stopped. Shorter reverberation times create a clearer sound environment, while longer reverberation times can contribute to a more lively and rich acoustics. Diffusion is another important concept, which refers to how sound waves spread in a room to avoid harsh reflections and create a more balanced sound image.

To block unwanted sound, sound-insulating materials such as dense panels, sound mats, and elastic suspension systems are used. These work by reducing the ability of sound to travel through walls and ceilings. On the opposite side of the spectrum are sound-absorbing materials, such as acoustic foam and mineral wool, which are used to reduce echoes and improve the sound environment inside a room.

When sound travels through different materials, it can be affected by resonance, which means that certain frequencies are amplified while others are dampened. This can be a problem in buildings where walls or floors can vibrate in time with certain sound frequencies. To minimize these effects, vibration-damping materials and techniques are often used to break the sound transmission.

Understanding and applying these acoustic principles makes it possible to create better sound environments in both work and home settings. By combining the right techniques and materials, you can effectively control sound levels, improve speech intelligibility, and create a more pleasant sound experience regardless of the context.

Acoustic concepts, abbreviations, and terms in sound insulation, sound absorption, and acoustics

Understanding basic acoustic concepts is crucial when it comes to sound insulation, sound absorption, and acoustics. Below is a summary of important terms and their meanings, providing a deeper insight into how sound works and how it can be controlled.

Absorption coefficient
The absorption coefficient is a measure of how much sound a material can absorb. It varies between 0 (no absorption) and 1 (complete absorption). Highly absorbent materials are often used in soundproofing measures to reduce reverberation and echoes in a room.

Acoustics
Acoustics is the science of sound, its properties, and how it is perceived. It encompasses everything from the production and transmission of sound to its impact in different environments, such as buildings, vehicles, and open spaces.

Acoustic impedance
Acoustic impedance describes the resistance that sound waves encounter when passing between different materials or media. Differences in impedance can affect sound transmission and reflection, which is an important factor in sound insulation.

Decibel (dB)
Decibel is a unit for measuring sound level or sound pressure level. A change of 10 dB is generally perceived as a doubling or halving of the sound level.

Diffusion
Diffusion means that sound waves are spread evenly in an environment to reduce reverberation and unwanted reflections. This is often achieved by using diffusing surfaces or materials that break up the sound waves.

Reverberation time (RT60)
Reverberation time is the time it takes for the sound to decay by 60 decibels after the sound source has stopped emitting sound. A short reverberation time creates a dry and clear sound image, while a long reverberation time provides a more lively and resonant sound, which is crucial in music studios, theaters, and conference rooms.

Frequency (Hz)
Frequency is measured in hertz (Hz) and describes the number of vibrations per second in a sound wave. Low frequencies produce bass tones, while high frequencies create treble sounds. Sound insulation and sound absorption are often tailored to specific frequency ranges to provide optimal effect.

Sound insulation
Sound insulation means preventing sound from being transmitted between different spaces. This is done by using sound-insulating materials, constructing dense structures, and minimizing sound leakage through walls, floors, and ceilings, for example.

Sound absorption
Sound absorption is the process by which sound energy is converted into heat instead of being reflected back into the room. This occurs when sound waves penetrate the porous structure of the material, reducing reverberation and improving the acoustics in a room.

Sound absorption
Sound absorption is a method of reducing sound reflection by using materials that effectively capture and dampen sound waves. This is often used in recording studios, theaters, and office environments to improve the sound environment.

Sound wave
A sound wave is a pressure wave that travels through a medium, such as air, water, or solid material. Sound waves can be longitudinal, where the particles vibrate in the same direction as the wave moves, or transverse, where the vibrations occur perpendicular to the direction of the wave's movement.

Sound attenuation
Sound attenuation means reducing the sound level by using damping materials or structures. This can be done through sound insulation, absorption, or diffusion, depending on the type of sound to be reduced.

Sound pressure level (SPL)
Sound pressure level is measured in decibels (dB) and indicates the intensity of the sound in relation to a reference level. The higher the sound pressure, the louder the sound is perceived to be.

Sound intensity
Sound intensity describes the perceived intensity of sound and is affected by both sound pressure and frequency. Two sounds with the same sound pressure can be perceived differently depending on their frequency content.

Sound-insulating materials
Materials used to reduce sound transmission through walls, floors, and ceilings. Examples include heavy boards, foam, sound absorbers, and flexible sound barriers such as SilentDirect MLV (Mass Loaded Vinyl).

NC (Noise Criteria)
Noise Criteria is used to specify and assess sound levels in different environments, such as offices and conference rooms. A low NC value means a quieter environment.

RT60 (Reverberation Time)
RT60 is a measure of the reverberation time in a room. Shorter RT60 values are recommended for office environments, while longer RT60 values can be beneficial in concert halls where the sound should fade out naturally.

Reflection
Reflection occurs when sound waves bounce off hard surfaces instead of being absorbed. Too much reflection can cause echoes and impair sound quality, while controlled reflection can improve the sound experience in music studios, for example.

Resonanceoccurs when a material or surface begins to vibrate at a certain frequency, which can amplify unwanted sounds. This is an important aspect of sound insulation, especially in vehicles, boats, and buildings.

STC (Sound Transmission Class)
Sound Transmission Class (STC) is a measure used to describe how well a building component, such as a wall, door, or window, reduces sound transmission between different spaces. The higher the STC value, the better the sound insulation. STC is measured by testing how much sound is attenuated at different frequencies and compiling the results into a uniform scale.

STC classes and their impact on the sound experience
STC values help predict how much sound passes through a structure. Here is an overview of different STC classes and how sound is perceived in them:

- An STC value between 25-30 means very weak sound insulation. Normal conversation and music can be heard clearly through the wall.

- An STC value between 30-35 provides limited sound insulation. Conversations can be heard but are somewhat muffled, and music can still be clearly perceived.

- An STC value between 35-40 provides moderate sound insulation. Loud conversations are audible but muffled, while muffled music can still be heard.

- An STC value between 40-50 provides good sound insulation. Normal conversations are difficult to hear and loud noises are significantly muffled.

- An STC value between 50-60 means very good sound insulation. Most sounds from neighboring rooms are effectively blocked, and only loud noises can be heard faintly.

- An STC value of 60+ provides excellent sound insulation. Almost total sound blocking, even loud noises are barely noticeable.

How does STC affect different environments?
Depending on the area of use, different STC levels are appropriate for achieving the desired sound comfort:

- Residential: STC 40-50 is common in multi-family buildings to reduce disturbances between apartments.

- Offices: STC 45-55 is often used in office buildings to ensure a quiet working environment.

- Hotels & hospitals: STC 50-60 is recommended to create a quiet and relaxing environment.

- Cinemas & studios: STC 60+ is required to minimize sound leakage and disturbances.

How can you improve the STC value?
There are several methods for increasing STC and thus improving sound insulation:

- Thicker and heavier materials: Concrete and solid wood walls naturally have higher STC values.

- Double plasterboard and insulation: Using two layers of plasterboard with insulation in between improves soundproofing.

- Resilient fasteners and sound-absorbing mats: These reduce sound transmission by absorbing vibrations.

- Sealing strips and sound-absorbing doors: Prevents sound from seeping through gaps and openings.

Conclusion
STC is an important factor in creating a comfortable sound environment. By choosing the right STC value for different building components, disturbing noise can be significantly reduced. For homes and workplaces, an STC value of 40–50 is often sufficient, while special environments such as studios and cinemas require 60+. By using the right materials and construction techniques, sound insulation can be optimized to meet specific needs.

Did you know that..

Did you know that certain acoustic terms are often misunderstood, which can lead to incorrect solutions to sound problems? A common example is the difference between sound insulation and sound absorption—where sound insulation is about blocking sound from passing through a wall, while sound absorption reduces reverberation within a room but does not prevent sound from passing through the structure.

Another misunderstood term is structure-borne sound, which is not the same as airborne sound. Structure-borne sound occurs when vibrations travel through the building's materials, allowing sound to be heard far from its source. Many people believe that thick carpets or sound absorbers solve the problem, but in reality, vibration-damping materials, such as rubber or decoupled structures, are required to break the sound's path. By understanding the difference between terms such as sound transmission, reverberation time, and resonance, you can choose the right measures and products to create a quieter and more comfortable environment!