CONSIDERATIONS REGARDING IMPACT SOUND INSULATION PERFORMANCES OF DIFFERENT FLOOR MATERIALS

Transcription

1 JAES_1(14)_1_2011 TAMAS-GAVREA D.R. et all, pp SECTION Civil Engineering and Installations CONSIDERATIONS REGARDING IMPACT SOUND INSULATION PERFORMANCES OF DIFFERENT FLOOR MATERIALS TĂMAŞ-GAVREA Daniela-Roxana 1, MUNTEANU Constantin 2 ARTICLE INFO Article history: Accepted: March 2011 Available online: July 2011 A B S T R A C T Impact noises are part of the structural noises, transmitted by the impact of one object against another, from a point through the entire structure, creating noise in many parts of the building. The vibrations generated by the impact can be propagated to adjacent rooms and then be radiated as airborne sound. The amount of the impact noise generated at the lower storey will be determined by the force of the impacting object, the vibration transmission characteristics and the covering floor materials. This paper presents an investigation of the acoustical insulation performances of different floor coverings against impact noise. Finally some results of the developed measurements will be indicated. Keywords: impact noise, acoustic insulation, floor covering INTRODUCTION Sound transmission through the floor is a common noise problem in school buildings. Impact noise within a classroom must be kept down to a limit that will not interfere with important processes like communication, attention and concentration developed during teaching activities. Therefore the major objective inside these rooms will be concerned on the attenuation of impact sounds which includes chairs or tables siding, shoes on the no carpeted floor, objects being dropped onto the floor to be transmitted into the spaces below through the floor. In accordance with SR EN ISO [1], the impact sound insulation performance between rooms measured in situ can be characterized by the normalized impact sound pressure level defined by the formula: 1 Ph.D. Student Teaching Assistant, Technical University of Cluj-Napoca, Faculty of Civil Engineering, Roxana.Tibrea@cif.utcluj.ro, Romania 2 Ph.D. Senior lecturer Eng., Technical University of Cluj-Napoca, Faculty of Civil Engineering, Constantin.Munteanu@cif.utcluj.ro, Romania

2 CONSIDERATIONS REGARDING IMPACT SOUND INSULATION PERFORMANCES OF DIFFERENT FLOOR MATERIALS L ' n A = Li + 10 lg (1) A ' where: L n is the normalized impact sound pressure level, in db, field measurements, L i is the measured sound pressure level, in db, A is the total sound absorption in the receiving room, in m 2, 2 A 0 is a reference absorption area ( A 0 = 10m ). In order to obtain a single number criteria which can be used as a performance indicator, the normalized levels obtained in 1/3 octave bands over the range 100Hz to 3150Hz are compared with the standard curve, according to the method presented in the international standard SR EN ISO [2]. The comparison consists in displacing the reference curve in steps of 1.0 db against the measured curve until the sum of unfavorable deviations is not greater than 32 db. It is considered that a deviation is unfavorbale at a given frequency when the measured values exceeds the reference values. Only unfavourable values will be taken into consideration. The value of the reference curve, expressed in db, at 500 Hz, following the mentioned procedure is L n,w. In this study measurements regarding impact sound insulation of different floor materials between vertically adjacent rooms where the receiving room is intended for study purposes will be presented. MATERIAL AND METHOD 1. Field Measurements The experimental determinations have been carried out according to the International Standard ISO [1], which describes the measurements procedure of the impact sound insulation properties of different materials used as floor coverings in schools. Impact noise can be measured using a standard tapping machine as a source with five hammers, each weighing 0.5 kg, arranged in such a way that they fall against the floor twice per second. Measurements are taken in the receiving room with the tapping machine turned on in at least four different positions over the existing floor system without a soft covering. The taping machine positions have been estabilished in order to fulfill the ISO requirements [1]. The main transmission path of the tapping machine s noise from the source room to the receiving room is represented by the floor system between the two rooms. Sound pressure levels and reverberation time decay are measured in the receiving room in 1/3 octave bands. The impact noise level in the receiving room can be attenuated by using over the existing 0

3 JAES_1(14)_1_2011 TAMAS-GAVREA D.R. et all, pp SECTION Civil Engineering and Installations floor different covering materials. Three floor covering materials used in residential and commercial buildings were investigated with the tapping machine disposed over the sample. All measurements were performed by using a Bruel&Kjaer acoustic equipment. 2. Existing Floor System The existing floor assembly for all samples tested has the structure described in table 1. Table 1. Floor system structure Floor covering Thickness (cm) Density (dan/m 3 ) 1. Laminated parquet Elastic layer Cement floor slab Concrete floor Mortar-cement plastering Floor Coverings Three types of floor finishes were evaluated: carpet, linoleum and rubber. The main characteristics of the materials are summerized in table 2. Table 2. Tested samples Floor covering Thickness (mm) Density (dan/m 3 ) 1. carpet linoleum rubber An image of the investigated samples is presented in figure 1. Fig.1. Measurements in source room.

4 CONSIDERATIONS REGARDING IMPACT SOUND INSULATION PERFORMANCES OF DIFFERENT FLOOR MATERIALS 4. Results Table 3 shows the values of the measured sound pressure level in the receiving rooms of the chosen samples. Table 3. Measured sound pressure level values Measured sound pressure level Frequency Laminated parquet (existing conditions) Carpet Linoleum Rubber In order to obtain the normalized impact sound pressure levels, all the measured values were corrected. Resulted levels are presented in figure 2. Fig.2. Normalized impact sound pressure levels in receiving room

5 JAES_1(14)_1_2011 TAMAS-GAVREA D.R. et all, pp SECTION Civil Engineering and Installations ' The weighted normalized impact sound pressure level L n,w calculated according to the method presented in the international standard SR EN ISO [1], is shown in figure 3. Fig.3. Weighted normalized impact sound pressure level values An image of the measurements developed in the receiving room can be seen in figure 4. Fig.4. Measurements in the receiving room

6 CONSIDERATIONS REGARDING IMPACT SOUND INSULATION PERFORMANCES OF DIFFERENT FLOOR MATERIALS CONCLUSIONS Impact sound transmission tests were developed in order to analyze the impact sound insulation performances of different materials used in schools. The comparison relieve that from the most commonly floor coverings used in educational buildings, the soft carpet ensure a significant reduction in impact noise at mid and high frequencies. Also, the rubber material may be beneficial in impact sound reduction but it is more expensive than the carpet. The studied linoleum layer doesn t provide a significant reduction of impact noise transmission. Field measurements shows that softer, less dense materials will absorb more impact noise than hard materials. REFERENCES 1. *** (2005), SR EN ISO 140-7: Acoustics Measurements of sound insulation in buildings and of buildings elements Part 7: Field measurements of impact sound insulation of floors, ASRO. 2. *** (2000), SR EN ISO 717-2: Acoustics Rating of sound insulation in buildings and of building elements Part 2: Impact sound insulation, ASRO. 3. *** (2005), C : Norms related to the design and implementation of sound insulation measures and of sound treatments in buildings. 4. MUNTEANU, C., TAMAS-GAVREA, D-R. (2011), Considerations on the adoption of the European standards on impact sound insulation in Romania, 11 th International Scientific Conference VSU, Sofia. 5. *** Norms related to sound protection. General provisions.