Tapping Machine Research Articles

Japanese standards of measurement method and rating for floor impact sound insulation

Among the objections and the troubles of buildings in Japan, the floor impact sound is one of the most serious issues. The floor impact sounds are classified in a heavy- and a light-weight floor impact sound by the characteristic of the impact source. One is the floor impact sound caused by human jumping, running, or walking and the other is the floor impact sound caused by falling lightweight object. The measurement and rating method for floor impact sound insulation is standardized in JIS (Japanese Industrial Standard). JIS A 1418-2 is method using standard heavy/soft impact sources, a car-tire source (a bang machine) and a rubber ball source. The heavy-weight floor impact sound insulation is started in Japan. JIS A 1418-1, which is corresponded to ISO140-7, is method using standard light impact source, a tapping machine. The evaluation for the floor impact sound insulation is standardized in JIS A 1419-2 which is corresponded to ISO 717-2. This paper summarizes the trends for the floor impact sound ins...

American Society of Testing Materials draft standard for rating in-room floor impact noise

In 2010 an ASTM subcommittee was formed to assess the possibility of rating the noisiness of different floor surfaces from impacts such as footfalls and dropped objects. Since that time the subcommittee has been meeting biannually to discuss potential impact noise sources and measurement techniques that could be used in a future standard. Different impact sources were evaluated including footfalls with different shoe types, golf balls, and the standard mechanical tapping machine. Both field and laboratory measurements were considered. This paper presents some of the preliminary test results that were obtained and the current status of the proposed laboratory standard.

Identification of Low-Frequency Forces Induced by Footsteps on Lightweight Floors

Despite many advantages of wooden buildings, low-frequency noise disturbance, mainly from human footsteps on timber floors, is a major hindrance for widespread application of wood in multi-storey buildings. In many cases the impact noise evaluations of the wooden floors according to ISO 140-7 and ISO 717-2 standards do not correspond to subjective experiences. This study aims to investigate the characteristics of footstep forces to support further studies related to discrepancies between standard evaluations and low-frequency noise disturbances in lightweight buildings. Transient footstep forces in vertical direction made by different walkers and different footwear on two floor structures were measured and compared. The vertical footstep forces were then compared with the impact forces made by a standard tapping machine. Analysis revealed that footstep forces contain large amplitudes at low frequencies (20 < f < 50) which are not included in the standard evaluation procedure. Therefore, by extending the frequency range of the standard measurements down to 20 Hz and designing an accurate adaptation term for evaluations, a better correlation between standard impact noise evaluations and acoustic performance of the lightweight buildings might be achieved.

The “dust spring effect” on the impact sound reduction measurement accuracy of floor coverings in laboratory

Standard measurement methods of impact sound insulation of floor coverings (resilient surface layers) in laboratory are stated on Standard ISO 10140 series. Laboratory test allows evaluating the acoustical performance of resilient surface layers in terms of reduction of impact sound pressure level ΔL. Resilient surface layers applied on the top of the structural reference floor effectively reduce the impact noise produced in the receiving room by a tapping machine excitation. In any case, an accurate characterization of the acoustical performances of the resilient surface layers depends on several boundary conditions. In this paper, it is shown a very relevant effect on the measurement accuracy, due to the cleaning condition of the structural reference floor. In particular it has been observed that the presence of sand and/or dust (in a very small quantity, i.e. of about 5g/m2) scattered on the bare slab greatly influences the experimental results. Researchers and technicians involved in building acoustic measurements in standard laboratories are well aware about the issues of proper cleaning, in particular if the resilient surface layers must be fixed on the surface by gluing. Nevertheless, the ISO 10140 standard (as well as previous ISO 140 standard series) does not state, as requirement, to glue the layers on the surface of the reference floor. As a consequence any accidental impurity on the bare floor surface can be a relevant source of inaccuracy.

Contribution of floor treatment characteristics to background noise levels in health care facilities, Part 2

Additional acoustical tests were conducted as Part 2 of a previous study [JASA 136(4), 2219–(2014)] on ten types of commercial grade flooring to assess their potential contribution to surface-generated noise within healthcare facilities. These floor samples utilized an ECORE ForestFX sheet vinyl wear layer and tested with rubber-backing thicknesses ranging from 2 mm–10 mm, plus a composite backing composed of two 2 mm layers. Two types of ECORE International adhesives, EGripIII and Evolve, were tested as part of the adhesive used during manufacturing as well as with local mounting of all floors on concrete substrates. Sound power tests were conducted in compliance with ISO-3741-2010 for two source types, an impact tapping machine and a rolling hospital cart. The sample that achieved the lowest radiated sound power levels for both the rolling cart and tap tests was Forest FX sheet vinyl with 10 mm rubber backing and Evolve adhesive. Two trends were observed. First, measured sound power levels reduced as backing thickness rose. Second, the Evolve adhesive demonstrated lower sound power levels for all tap/rolling tests when compared with those utilizing the EGripIII adhesive. The suitability of using thicker floor backings in healthcare facilities are discussed. [Work supported by Paul S. Veneklasen Research Foundation.]

Measurement of Walking Noise on Floor Coverings

Walking on floors in buildings generates noise in the room where the walking takes place. Manufacturers of floor coverings are interested in stating characteristic walking noise levels for their products. Recently, the European standard EN 16205 introduced such a measurement procedure. It is based on the former French standard NF S 31-074, but tries to solve the prevailing ‘self-noise’ problem of the walking noise source used (the ISO tapping machine) in a simpler and theoretically more correct way. To evaluate the EN method, a round-robin test with 17 European laboratories was carried out. The measurement methods of NF S 31-074 and EN 16205 and the round-robin test are presented here. It was found that EN 16205 works quite well with louder floorings like laminate and PVC. Soft and quiet floorings like carpets are more difficult to measure because their noise contribution disappears behind the noise of the ISO tapping machine.

Estimativa de incerteza em ensaios de ruído de impacto: posição dos equipamentos em medições em campo

A precisão metrológica em ensaios em campo de acústica de edifícios é uma questão atual, com necessidade ampla discussão sobre as variáveis envolvidas que podem gerar dúvidas nos resultados. Nesse contexto, este trabalho analisa as incertezas de medições de ruído de impacto em campo. O foco do trabalho é a análise da influência do posicionamento dos equipamentos. As medições foram realizadas conforme as normas ISO 140-7 e ISO 140-14 em duas salas sobrepostas, separadas por uma laje de concreto maciço de 10cm de espessura. Foram consideradas dois grupos de variações no posicionamento da máquina de impactos e do microfone: distâncias mínimas das paredes definidas nas normas ISO e pontos centralizados no piso. As variações no posicionamento dos equipamentos geraram 64 resultados de níveis sonoros na sala de recepção, divididos em quatro grupos de resultados, a partir das medições na faixa de frequência entre 100 e 3.150 Hz. Para as análises foram utilizados os métodos da norma ISO 12999-1 e do Guia RELACRE/Portugal que expressam de formas diferentes as incertezas de medições acústicas em edificações. Os resultados são apresentados na forma de exemplos de aplicação em sistemas pisos ensaiados anteriormente, com diferentes comportamentos acústicos e consequentemente, com valores distintos de níveis de ruído de impacto padronizados ponderados corrigidos pela incerteza estimada. Neste estudo foi evidenciada e quantificada a influência do posicionamento dos equipamentos nos resultados de ensaios de ruído de impacto em campo.

Impacted lightweight stairs as structure-borne sound sources

The requirements and methods of characterising impacted lightweight stairs as sources of structure-borne sound and of predicting the resultant sound pressure in buildings are described. The approach is to treat the stair system and the excitation as a single active source. In this study, the stair is excited by a tapping machine or an instrumented shaker, although the approach lends itself to the use of walkers ascending and descending the stair. The approach provides laboratory data suitable for prediction of the structure-borne power transmission from the stair to the supporting wall in a building and thence the resultant sound pressure in adjacent spaces. For the case studied, the primary transmission path is through a bolt to a supporting wall, which also is the separating wall between dwellings. This is a common situation in Germany. The source data can be the velocity of the free source at the contact point and the associated point mobility. Alternatively, a reception plate method is considered, which yields the source power. The approaches provide laboratory data appropriate for prediction of the resultant sound pressure in adjacent rooms using existing building propagation models. By comparison of predicted and measured sound pressure levels, the achievable accuracy is assessed and sources of uncertainty are highlighted.

Contribution of floor treatment characteristics to background noise levels in health care facilities, Part 1

Acoustical tests were conducted on five types of commercial-grade flooring to assess their potential contribution to noise generated within health care facilities outside of patient rooms. The floor types include sheet vinyl (with and without a 5 mm rubber backing), virgin rubber (with and without a 5 mm rubber backing), and a rubber-backed commercial grade carpet for comparison. The types of acoustical tests conducted were ISO-3741 compliant sound power level testing (using two source types: a tapping machine to simulate footfalls and a rolling hospital cart), and sound absorption testing as per ASTM-C423. Among the non-carpet samples, the material type that produced the least sound power was determined to be the rubber-backed sheet vinyl. While both 5 mm-backed samples showed a significant difference compared to their un-backed counterparts with both source types, the rubber-backed sheet vinyl performed slightly better than the rubber-backed virgin rubber in the higher frequency bands in both tests. The performance and suitability of these flooring materials in a health care facility compared to commercial carpeting will be discussed. [Work supported by Paul S. Veneklasen Research Foundation.]

Comparison of the Standard Floor Impact Sound with Living Impact Source by Subjective Evaluation

In the previous test, the verification of the standard floor impact source was carried out comparing the physical characteristics with living impact sources. The result was appeared the validation of the standard impact source was very low because of differences of physical characteristics. This study aims to evaluate annoyance and loudness of standard impact source which is used for the measurement of floor impact sound, and to compare the annoyance and loudness of living impact sources which are produced in real life. The impact sources considered are tapping machine, tire and impact ball as standard sources, and nine real sources which were chosen from the existing researches. The result showed differences of annoyance and loudness between standard impact sources and living impact sources, which means the standard impact sources may rate the performance of floor system inappropriately. In the future, the rating method should be examined how the standard impact sources are similar with real sources in the point of rating the performance of floor system.

실생활 충격소음을 통한 표준 바닥충격원의 실효성 검증

The standard impact sources, standardized to rate the sound insulation performance of floor structure, should simulate well the real floor impact sources, which is very important to grade the floor structure then to establish counter plan to improve the performance of floor. Recently the tire, the standard heavyweight impact source, has been discussed that the impact force is too big to represent the real impact force. And researches have been carried on the applicability as a substitute or a supplementary. In addition, tapping machine, the standard lightweight impact source, is also questionable if it is representative of real lightweight impact source. This study aims to examine the similarity of standard impact sources with living impact sources, comparing the physical characteristics such as impact force, frequency contents and sound level. The result showed that the physical characteristics of standard impact sounds were somewhat different with that of living impact sounds, and the standard sources couldn`t be verified from this result. Later subjective evaluation should be followed to compare how the physical differences make relationship with the subjective differences.

Development of a low-frequency impact noise metric

Low frequency footfall noise (“thudding”) is a common source of complaints in lightweight joist-framed multifamily projects. Previous work by the authors has indicated that the low frequency impact sound pressure levels (LFISPL) from a standard ISO tapping machine are highly correlated with occupant reaction [LoVerde and Dong, J. Acoust. Soc. Am. 112, 2201 (2002), LoVerde and Dong, INCE Inter‐Noise 2004 Proceedings, 167 (2004)]. In order to be useful, the raw LFISPL must be translated into a single number that maintains the high correlation with subjective reaction while providing adequate dynamic range to distinguish the performance of different assemblies. Candidate metrics are evaluated.

Subjective and Objective Evaluation of Impact Noise Sources in Wooden Buildings

Multi-storey timber buildings up to 6 and more floors are increasingly built in many European countries. The challenge with these buildings can be that with traditional intermediate floor constructions in timber it can be difficult to fulfill the standard requirements and even when they are met, low frequency transmission can still cause complaints. Additionally it is difficult to develop appropriate light weight floor constructions since it is well known that the correlation between the standardized evaluation methods using the tapping machine and the human perception of impact noise can be poor, especially in buildings with light weight structures. In the AcuWood project, measurements and recordings on different intermediate timber floor constructions in the laboratory and the field were performed covering a wide range of modern intermediate timber floor constructions. Additionally, one intermediate concrete floor with different floor coverings was included in the study. Besides the standardized tapping machine, the modified tapping machine and the Japanese rubber ball and “real” sources were employed. Subjective ratings from listening tests were correlated to many technical single number descriptors including the standardized descriptors and non-standardized proposals. It was found that the Japanese rubber ball represents walking noise in its characteristics and spectrum best, taking into account the practical requirement of a strong enough excitation for building measurements. The standardized tapping machine, with an appropriate single number descriptor, L′nT,w + CI,50-2500 or slightly better, L′nT,w Hagberg 03, leads also to an acceptably high determination coefficient between the descriptor and the subjective ratings. Additionally, the study delivered data, from which proposals for requirements for the suggested single number ratings are deduced, based on the subjective ratings.

The Tapping Machine Mathematical Modeling Simulation Study

Based on the tapping machines special structural features and practices, from both directions of rotation and impact established the tapping machine mechanism rotating borer and impact dynamic mathematical model, analysed the effect of different tapping machines parameters on the model itself, simulated the model with inputting wide pulse signal, the simulation results show that: firstly, the tapping machine model established in this paper is reasonable; secondly, increase the damping coefficient of the blast furnace, the tapping machines rotating borer rotation speed and impact attenuation speed decrease.

On the relevance of impact source impedance at low frequencies

Many researchers have posed the question of whether the standard tapping machine simulates the impedance of real sources well enough to properly judge the impact sound insulation performance of a floor. Proposed solutions such as the modified tapping machine, the bang machine, and ball were results of these investigations. Recent data collected on bare (wood and concrete) floors, suggest that in the low frequency range, the impedance of the source has no influence on the power injected into the floor. This is presumably due to the fact that the bare floors have much higher impedances than most common sources, meaning only the blocked force of the source influences the injected power. This furthermore suggests that modifying or redeveloping the source is not necessary, and that through use of an appropriate weighting curve a single number rating that correlates well with subjective measurements can be defined. Supporting objective and subjective results will be presented.

신축공동주택의 상하층간 소음 및 진동전달 특성과 층간소음 차단성능에 관한 연구

This study involves 2 newly built apartment houses which are A with 23 floors as 150 mm slab width and B with 16 floors as 180 mm slab width. The impact was added by tapping and bang machine at the middle floor level of these 2 apartments and the test was arranged in terms of the characteristic of vibration and sound level which transferred to upper or down floors. As a result, impact floor shows the highest value in terms of both sound and vibration level and followed was at down floor of the Impact floor. Also, blocking function for the lightweight and heavyweight floor impact sound level was tested for each room of the apartment A and B including living room, main room, room 1 and 2. As a result, sound blocking function of B apartment was better than that of A and the function was getting worse when the room size is getting smaller.

Study on Oblique Cam Type Mechanical Torsional Vibrator

Vibrator is the key part of vibration tapping machine. In this paper, a kind of oblique cam type mechanical vibrator was designed. The vibrator has the advantages of simple structure and easy manufacturing, and the output amplitude of the vibrator can be adjusted by changing the inclination angle of oblique cam. It is verified by experiments that the process is successful when the oblique cam type vibrator is used to machine big thread holes, and compared with common continuous tapping, the torque of vibration tapping decreases significantly.

Acoustic contributions and characteristics of floor treatments for elementary school classroom background noise levels

A two part investigation involving the effect of floor treatments on classroom background noise levels will be presented. Phase 1 determined the effects of hard versus soft flooring on overall speech and activity noise levels using long-term calibrated sound recordings in elementary classrooms. Two similar-sized classrooms were used: one with vinyl composition tile (VCT) flooring, and one with short-pile commercial carpeting. After parsing the recordings into separate segments of (a) teacher/student speech (alone), and (b) classroom activity noise, including footfalls, chair scrapes, and impacts (no speech), a significant decrease in overall levels was found in the carpeted rooms. Phase 2 determined the acoustical properties of nine different flooring materials ranging from resilient athletic floors to VCT to commercial carpeting. Sound absorption was measured following ISO 10534-2, while ISO 3741 sound power measurements were made while either (a) using a standard tapping machine, or (b) scraping a classroom chair back/forth over the floor surface in a reciprocating manner. In general, both carpet samples resulted in the lowest sound levels and the highest absorption. Relative performances of each material will be presented along with additional classroom usability factors, such as maintenance, cost and durability. [Work supported by Paul S. Veneklasen Research Foundation.]

A two domain method for design and evaluation of floor-ceiling assemblies using tapping machine impact sound pressure levels

Structure-borne impact noise from footfalls is a common noise complaint in multi-family residential buildings, and is currently described by a single-number metric such as IIC (using a tapping machine) or LA max (using an impact ball). However, research indicates that impact noise is characterized by two independent frequency domains: low frequency thudding and mid- to high-frequency noise from heel clicks, etc. The levels in these two domains vary independently with assembly design, so that two parameters are required to adequately characterize the impact insulation of an arbitrary assembly. The authors have developed a two-parameter system for evaluating impact noise [LoVerde and Dong, J. Acoust. Soc. Am. 122, 2954 (2007), J. Acoust. Soc. Am. 125, 2708 (2009)] intended to improve the design and evaluation of floor ceiling assemblies. Over the past 7 years, this system has been applied to design, evaluation, and testing of many projects. Criteria have been developed, and the real-world use of the proposed system is described, evaluated, and compared with the existing metrics.

Rating the impact sound insulation of flooring from its airborne sound reduction index

With the increasing adoption of higher density forms of dwellings in urban environments we need reliable but economic means of verifying that they meet specified sound insulation requirements. This is particularly so now that territorial and building code authorities are realising that performance checking is an indispensible part of the quality assurance process. This presentation concerns a simplified way of confirming the impact noise insulation in buildings. This makes impact sound insulation rating possible without the need to make impact sound pressure level measurements. The technique estimates the impact sound level by using an accelerometer attached to a hammer (similar to those used in the standard tapping machine) to measure the reaction force from the floor and combines this with the floor's sound reduction index. The method simplifies the equipment required for impact sound insulation rating and allows measurements to be made in the presence of high background noise.