Acoustics in Rooms and Buildings

Datum: 2011-11-28
Publicerad: Svensk Byggtjänst 1983
Artikelförfattare: Lennart Karlén

Acoustics are important in the entire building process. The acoustic environment in a building is not only dependent on the properties of the room-forming materials, but it is also affected by the placement of the building on the lot, the foundation, framework, floor plan, etc. Acoustics in Rooms and Buildings is about project planning divided into the following areas:

- programme stage
- system action stage
- construction action stage
- inspection
- use

In the book, there are examples of practical, applicable solutions in a normal construction project. Between the stages there are checklists, and summaries of standards and material data are presented in appendices. The chief author is M.E. Lennart Karlén, who has many years’ experience in the field of acoustics in construction project planning. One chapter on project planning methodology is written by Professor Olle Wåhlström.

This book is only available for download in Swedish.

Vibration isolation on weak and finite support - a model and parameter study

Datum: 2010-05-12
Publicerad: BNAM Conference 2010
Artikelförfattare: Peter Blom

The article describes a model handling of vibration isolation on weak and finite supports. Moreover, examples of experimentally obtained model data and input data are provided.

The walls around the orchestra at Stockholm Concert Hall

Datum: 2010-04-19
Publicerad: Bygg & Teknik 3/10
Artikelförfattare: Lennart Karlén

A concert hall is designed for its functions in many aspects and for many different activities. The Great Hall at Stockholm Concert Hall has an advantage in that it is the place of residence of the Royal Philharmonics and is foremost designed for their needs. Such a special room as the stage in a concert hall is the heart in the acoustic function for the whole hall. Its design sets the conditions for the orchestra and for how the sound will spread out to the audience. The orchestra’s needs are multifaceted. They have to work in a group, the instrument group, and at the same time hear themselves. Additionally, the instrument group is to form an integrated part of the whole orchestra.

Heat recycling

Datum: 2009-08-13
Publicerad: Bygg & Teknik 5/09
Artikelförfattare: Lennart Karlén

Energy prices are driving developments that in the long run may provide us with interesting technical solutions, where the transformation of energy is integrated in the normal parts of the building's system. It seems that solar cells and solar panels may be developing in that direction...

The full article is available in Swedish only.

Generation of forces and vibrations by fans

Datum: 2009-04-20
Publicerad: Bygg och teknik 3/09
Artikelförfattare: Peter Blom

One aspect that has not been extensively explored is disturbances from the fans in the form of vibration. These disturbances are forces that generate vibration in surrounding structures and ultimately give rise to audible building vibration. The fan is often mounted on a vibration insulator made of rubber or in the form of a steel spring. In order to be able to dimension the insulation correctly, one must gain access to information about the absolute force levels. A commonly used type of fan for ventilation application is the centrifugal fan, which in principle can be designed in three ways – with radially directed, backward- or forward- directed blades. In this study, measurements and analysis were performed on fans of centrifugal type with backward- directed blades.

This article is only available for download in Swedish.

Practical Modeling of Vibration Isolation on Weak and Finte Supports

Datum: 2008-09-15
Publicerad: BNAM2008 Reykjavik
Artikelförfattare: Peter Blom

1. INTRODUCTION
An approach to estimating the vibration isolation machines on weak and finite supports is discussed in principle. The model should hold inversely and be able to predict the forces acting on the foundation from the measured motion; data often requested by constructors. The novelty lies not in the utilized theory but rather in the endeavor of creating a base model that can be improved along the way and adapted to various situations, thus providing tenable solutions without resorting to constructions with unnecessarily high safety factors.

2. THE MODEL AND ITS PARAMETERS
The model relies on the different impedances inherent to the system, primarily the point impedances. In its simplest form this involves the impedance of the source (the mass), the isolator (the stiffness) and the support. For an existing support, finding the impedance is readily done through an impact excitation. Adopting the resulting data in the model, the resonant characteristics of the support are captured.
For nonexistent structures the impedance needs to be calculated beforehand. Specifying the boundary conditions and characteristics of the structure and assuming mode shapes, the modal mass and eigenfrequency can be calculated-it turns out that in practice it is often the lowest mode that is of interest since the dispersive characteristics of bending waves bring the higher eigenfrequencies well above the excitation frequency. The eigenfrequencies are obtainable through regular formulas for simple structures that often work well as approximations. Once the eigenfrequency and modal mass are established, the support can be modelled as a simple mass spring system whose impedance shows a resonance dip. Next, setting up the equations for the vibration isolation is straightforward.

3. EXTENDING THE MODEL
There are various aspects related to the impedances in this model that can be developed further:
Rubber is an often used material for vibration damping. Due to its complex characteristics standard formulas relying on static stiffness is likely to produce large errors. The more so the higher the frequency since viscoelasticity is proportional to the strain rate. A suitable way to model viscoelasticity is through fractional derivatives that in the frequency domain becomes a handy method.
A second rubber feature to be incorporated is the amplitude dependent non-linearity referred to as the Fletcher-Gent effect. This phenomenon proves to be especially important for low frequencies where displacement amplitudes are normally high.
In a foreseeable future smart materials should be on the market even for rather simple applications; extending the model to cover such isolators is a natural step as the demand for such solutions will increase.
When structures are complicated the modal mass and stiffness should be evaluated through FEM calculations.

Acoustics in Restaurants

Datum: 2008-04-09
Publicerad: Bygg och Teknik 3/08
Artikelförfattare: Lennart Karlén

It is common knowledge that you to be able to eat and digest your meal properly you need calm and harmonic surroundings. And if you are in the company of family and friends that adds even more to the positive experience. These needs are fundamental and lack of them could lead to stress, bad food digestion and increased risk of various health problem.

This article is only available for download in Swedish.

Multi-dimensional Acoustic Project Planning of Rooms

Datum: 2007-08-10
Publicerad: Bygg och Teknik 3/07
Artikelförfattare: Lennart Karlén

For a room to sound right, you have to plan the room with regard to all of its acoustic characteristics. These include, in addition to length, width and height, time in the form of frequency, arrival time of reflexes to the ear, resonance and the loudness of the sound in its different directions of propagation. Yet another dimension...

This article is only available for download in Swedish.

Ventilation - Acoustics: When CAD Programs Are Not Enough

Datum: 2007-08-09
Publicerad: Bygg och Teknik 3/06
Artikelförfattare: Lennart Karlén

It has gotten better. Although noise from ventilation is one of the most common complaints about interior environments both in homes and workplaces, things have gotten better. We read of the Work Environment Authority’s inspections of schools and day-care centres in the newspapers. It is noise from...

This article is only available for download in Swedish.

Energy Utilisation in Commercial Buildings – Comparison between Buildings of Different Ages

Datum: 2006-05-01
Publicerad: Bygg och teknik 5/05
Artikelförfattare: Lennart Karlén

For some years, we have studied the utilisation of energy in commercial buildings for one of Sweden's major real estate companies. The purpose of this job was to formulate evaluation and comparison methods that could be used to control operations on a monthly basis, be able to compare years, get fast responses to measures and also be able to compare different properties in different...

This article is only available for download in Swedish.

Open Offices – New Trend?

Datum: 2006-04-01
Publicerad: Bygg och Teknik - 3/05
Artikelförfattare: Lennart Karlén and Anders Schönbeck

For some time, building open offices has enjoyed renewed popularity. It seems to have been a trend since the mid-90’s. Many large open offices were built during the 1970’s. Quite a bit of work was done at the time to study how offices should be designed for optimal function and comfort. Interior decoration, lighting, materials and, not least, acoustics were studied. No unequivocal answers to these questions…

This article is only available for download in Swedish.

Pre-fabricated Framework and Acoustics

Datum: 2006-03-01
Publicerad: Bygg och teknik 3/04
Artikelförfattare: Lennart Karlén and Anders Schönbeck

We have for many years worked in the field of the control of sound-proofing and step sound levels in buildings with prefabricated frameworks. This has been a question of concrete - concrete frameworks or frameworks of combined steel - concrete. In many projects, measurements provide approved values directly, in others there may be deficiencies. In these cases, our job has...

This article is only available for download in Swedish.

Comfort Is Equal to the Qualitative Perception of the Indoor Climate

Datum: 2005-06-01
Publicerad: Bygg och teknik 1/93
Artikelförfattare: Lennart Karlén

The indoor climate is comprised of all of the conditions that affect us in a room and in a building. We interpret effect, among other ways, through our senses, to form a perception that either gives the sensation of comfort or discomfort. Other effects that are not directly perceivable...

This article is only available for download in Swedish.

Indoors climate and comfort

Datum: 2005-05-01
Publicerad: Fastighetsförvaltaren 2/04
Artikelförfattare: Lennart Karlén

Indoor Climate and Comfort Often Receive Low HCI (Happy Customer Index) Values
In recent years, we have had contact with building owners who work with some type of quality development of their work and their buildings. We can establish that they are in a good position in the so-called HCI, the Happy Customer Index, but they always get low values for indoor climate. We have been commissioned to work with several of the companies to improve...

This article is only available for download in Swedish.

Ventilation Noise – the Most Common Complaint about the Indoor Environment

Datum: 2005-04-01
Publicerad: Bygg och teknik 3/93
Artikelförfattare: Lennart Karlén

Why are ventilation plants always noisy? They make noise both indoors and outdoors in spite of the fact that most people want buildings to be quiet. In this article, we offer a few ideas on the cause and proposals for...

This article is only available for download in Swedish.

Energy and Windows

Datum: 2003-06-01
Publicerad: Fastighetsförvaltaren 6/03
Artikelförfattare: Lennart Karlén

Windows are the main source of heat leakage in a normal building. Older 2-glass windows with a U-value (W/m2 °C) of around 3 mean that they release 10 times more heat energy than a normal exterior wall with a U-value of 0.3 for the same area. 2+1-glass windows usually have U-values of 1.5 - 2. Windows developed in recent years...

This article is only available for download in Swedish.

Condensation in Intake Ducts – A Technical or a Hygienic Problem?

Datum: 2003-05-01
Publicerad: Bygg och teknik 5/93
Artikelförfattare: Lennart Karlén

Outdoor air intakes and the portion of the duct between the exterior wall grate and the fan unit are cooled to temperatures below the dew point. Water vapour then condenses on the outside of the duct and can cause problem in the fan room. A commonly used method for avoiding condensation is...

This article is only available for download in Swedish.

Longed-for Freedom from Disturbance in Residential Buildings Is Being Developed

Datum: 2002-02-01
Publicerad: -
Artikelförfattare: Lennart Karlén

In all surveys on the wishes and expectations of people with regard to their homes, two characteristics top the list. These are security and freedom from disturbance. At the same time, one of the most common complaints in housing is disturbance from noise: noise from ventilation, traffic, neighbours, construction work...

This article is only available for download in Swedish.