What's the Difference Between Sound-Absorbing and Sound-Insulating?

Two distinct but interconnected areas of intervention: what’s the difference between sound-absorbing and sound-insulating?

In these pages, we will address solutions applicable to noise problems, and more specifically, interventions for sound insulation and sound absorption.

Sound insulation deals with containing disturbing sounds and noises generated within an environment, or reducing those that penetrate it.

Sound absorption, on the other hand, through acoustic treatment of surfaces, provides for the elimination of annoying echo and reverberation phenomena within an environment.

Unfortunately, when browsing online, you often encounter manufacturers, retailers, stores, or even entire marketplaces that confuse terminologies and create significant misunderstandings.

Are Sound-Absorbing Panels Soundproof?

If I Put Up a Sound-Absorbing Picture, Can I Listen to Records at Night?

We are asked these questions daily, and even if you’ll always find someone online saying “sound-absorbing panels are used for acoustic isolation,” the answer to all of these is “NO”!

Sound-absorbing panels absorb sound, they do not isolate from internal or external noises: they are used to eliminate annoying reverberation or reduce internal noise and only partially contribute to sound insulation, for which, instead, there are specially designed sound-insulating materials.

When to Resort to Sound Insulation

It is necessary to resort to sound insulation interventions when you want to achieve an improvement in privacy conditions through a significant reduction of acoustic energy entering or leaving a confined environment.

Materials with acoustic performance that allow achieving these levels of insulation are readily available in the building products market. These are massive sound-blocking materials, such as lightweight concrete, plasterboard, and many other composite and layered products with which it is possible to create new structures, false walls, false ceilings, coatings, and floating floors.

We are therefore talking about expensive interventions that are not always simple to execute because they may involve modifying existing windows, doors, and systems and reducing room dimensions, requiring the intervention of various professionals and the request for authorizations. Sometimes they can even compromise the habitability conditions of a room.

There are also particular noises that are transmitted essentially through mechanical means, causing the building structures themselves to vibrate. To eliminate them, it is necessary to perform an in-depth study of the acoustic bridges that transmit the noise to be isolated and use specific resilient and decoupling products such as joints, elastic supports, and rubber sheaths.

The range of cases is vast, and each situation calls for specific reference regulations. These are different, for example, if dealing with vehicular noise from outside or anthropic disturbance between residential units.

Once the source and path of the disturbing sound or noise have been determined, to guide the choice of materials, it is essential to know by how much we want or need to increase the sound insulation index value of our room: this technical parameter is among the passive acoustic characteristics that define the quality of a building.

After the work is completed, we will find ourselves in a well-insulated room but with completely reflective surfaces and therefore very reverberant, impossible to use as is for living and even less for musical practice or work uses. In fact, all the acoustic energy we generate in the room, having no more outlet, will be entirely preserved inside it.

This is where sound absorption will necessarily come into play.

When to Resort to Sound Absorption

A sound absorption intervention, also known as acoustic treatment, is essential in all situations that require an improvement in acoustic comfort conditions, or when reverberation and echoes compromise the usability of an environment.

It is achieved by covering structures with porous sound-absorbing material or by inserting elements into the environment such as the sound-absorbing panels of the AkuPan® series, which are capable like no other product of capturing acoustic energy and transforming it, dissipating it as heat.

How can we know how much sound-absorbing material we need to obtain a sufficient improvement in the acoustics of a room?

In technical acoustics, two fundamental parameters are referred to: the reverberation time RT60 and the Speech Transmission Index (STI). The latter is essentially reserved for classifying environments dedicated to communication and teaching, requires complex experimental analysis, and is not easily estimated through theoretical predictive calculations.

Therefore, we primarily focus on the study of reverberation time RT60, an acronym that includes “Reverberation Time” and the number 60, which represents the reference value in dB for this measurement of sound decay in an environment.

RT60 is measured in seconds and indicates the time needed for the reverberation of an impulsive sound in a confined environment to decrease by 60dB. This parameter is an index of the acoustic quality of an environment, and generally speaking, we can say that the higher the RT60 value, the more tiring the acoustic experience of an environment will be.

The RT60 value is easily measurable experimentally with minimal instrumentation. Moreover, thanks to the formulas developed by American physicist W. C. Sabine, it is possible to develop reliable predictive calculations based on knowledge of a few details related to the architecture of the rooms and the sound absorption coefficients of the acoustic treatment products we intend to use.

In this field, there is extensive literature and constantly evolving technical reference standards that help in identifying the most correct values to seek for this parameter, also in relation to the size and nature of the rooms, to optimize their internal acoustics.

There are fewer strict regulatory references which, to date in Italy, are limited to the field of school construction, providing rather generic guidelines and constraints.

Knowing the current reverberation time value of the environment, and having identified a reference target to reach for this parameter based on the intended use, an expert technician is able to quantify the correct size and type of sound-absorbing panels to be inserted in the environment to solve any type of acoustic comfort problem.

What sound insulation and sound absorption have in common

Let’s now briefly mention the interactions between sound insulation and sound absorption interventions.

First, we can explain a phenomenon that many HiFi enthusiasts know well: rigid, not particularly heavy coating structures, such as plasterboard, are said to “cancel out low frequencies“.

This is not entirely accurate. However, it is true that this sound-insulating material is effective in preventing the medium and high-frequency component of sound from transferring to the outside, while it is much less efficient in retaining the low-frequency component, whose energy escapes to the outside, resulting in the apparent sound absorption of these frequencies.

Secondly, we must emphasize the importance of improving the sound-insulating effect given by some types of sound-absorbing elements, particularly high-performance ones such as the sound-absorbing panels of the AkuPan® series or products derived from it.

In the theoretical calculation of the acoustic insulation index of environments, the RT60 reverberation time value of the disturbed environment is fully included. The lower this value is kept, the higher the acoustic insulation index will be. The relationship between these two quantities allows for an improvement of 6dB in the sound insulation capacity of structures through a 75% reduction in reverberation time.

Equally advantageous can be the insertion of our sound-absorbing panels AkuPan®, the most efficient internationally, certified by the University of Ferrara, in the disturbing environment. With just a few square meters of paneling, it is possible to halve the acoustic pressure developed inside a room because, by acting on the acoustic wave, they reduce at the source the energy that could propagate outside, decreasing the intensity of the disturbing sound or noise.

The incremental values of acoustic insulation obtainable using only high-performance sound-absorbing products that are active in a wide frequency band, such as the panels of our AkuPan® series, allow for solving or significantly attenuating most domestic noise problems with maximum simplicity. The intervention band will depend on the thickness of the panels: to absorb low frequencies, thicknesses from 10 cm upwards will be required.

Thanks to acoustic treatment alone, we can, for example, converse or listen to music without excessively disturbing the neighbor and, at the same time, we will be less disturbed by footsteps on the floor above or when children play or study the flute in the next room.

All this within the limits of the “volumes” of noises kept in the rooms, because true sound insulation is achieved with sound-insulating materials rather than sound-absorbing ones. For this reason, it is incorrect to speak of “sound-insulating panels”: there is no product in the world that, placed like a picture on the wall, can protect us significantly from external noises.

The installation of AkuPan® sound-absorbing panels is easy, economical, and risk-free, can be done independently, and does not require any type of authorization.

It is an intelligent first intervention solution even in complex situations because, even if it should not be sufficient to completely eliminate the problem, it will in any case be useful to improve the acoustic comfort of the environments, and can be integrated without problems with any further intervention that may be necessary.

EXAMPLE:

Let’s consider having to reduce the disturbance we cause to our neighbor when we play the violin.

From literature, we know that the instrument is capable of generating a maximum acoustic pressure of 80dBA.

We must then know the value of the apparent sound reduction index (R’w) of the separating elements between the two distinct real estate units in question, which we can assume to be 50dB, provided that the construction of the building is subsequent to the DPCM of November 14, 1997, which sets this value and requires builders to ensure compliance.

Finally, we must consider the maximum allowed differential input value, that is, how much of the violin sound is permissible to be heard in the neighbor’s home. For residences, the same regulation sets this value at 5dBA during daytime hours (from 6 am to 10 pm). In reality, the allowed sound input values refer to a time average over the hours of practice on the instrument, during which the peak value is rarely reached. In this example, we could consider an average value of the acoustic pressure developed by the instrument of 74dB A, 6dB lower than the peak value.

At this point, a quick calculation would show that it is necessary to increase the acoustic insulation value of our environment by about 20dB to be certain of not incurring problems or sanctions.

Achieving sound insulation values of this magnitude to isolate, for example, the noise of small machinery would be relatively simple, but to be certain of isolating the sound of a musical instrument as in the example, it might be necessary to create a ‘room within a room’ by covering all surfaces, including the floor, with a layer of acoustically insulating material with Rw coefficients of at least 20dB. This is to avoid neglecting any structural acoustic bridges present in the building that could render the covering of only the wall separating us from the neighbor completely useless.

Once the room is isolated, we will need to insert some sound-absorbing elements that will allow us to obtain optimal acoustic comfort for practicing the instrument and which, in turn, will further improve its sound insulation.

With just 5 high-efficiency AkuPan® sound-absorbing panels measuring 180x120cm in an empty 10 sq.m room with a height of 270cm, it is possible, for example, to eliminate 75% of reverberation and achieve a reduction in sound pressure of over 6dB. We could install these elements even before considering implementing acoustic insulation in the room, and verify if the increase in isolation obtained with sound absorption alone is already sufficient to avoid complaints from neighbors, saving us from more demanding work.

Oudimmo Free Consultation Service

Oudimmo Acoustic Design offers a professional free acoustic consultation service for evaluating noise problems and identifying possible solutions. To access the service, simply send a scaled floor plan and, if possible, some photographs of the problematic areas. Based on this information, we will develop a calculation to estimate the current RT60 reverberation time and can identify the correct quantity and sizing of high-performance products needed to achieve an effective improvement in your acoustic comfort.

Thanks to the high efficiency of our AkuPan® panels, which is up to 60% superior to common sound-absorbing products, we can offer you the best and most suitable solution, without any commitment on your part.

And if it turns out to be essential to immediately pursue the path of sound insulation with certainty of results, we can put you in touch with professionals in the field in your area for a consultation.

Who is talking about us:

https://www.bergamonews.it/dal-territorio/il-mio-ristorante-preferito-e-troppo-rumoroso/

https://www.lavorincasa.it/pannelli-fonoassorbenti/

Who uses Oudimmo Acoustic Design sound-absorbing acoustic panels: CNR, Cinecittà, Panasonic, Lamborghini Automobili, Unicredit, Ristò, Bticino, ABB, Poste Italiane, Verdena, DJ Prezioso, Aimart (International Academy of Music and Art) and many others.