Keywords

1 Introduction

The speed of sound waves varies depending on the medium. The speed of sound in an atmosphere of 20 Â°C is about 343 m/s, and the transmission speed of sound through solids is much faster than air. When sound waves are transmitted from one interface to another, they are reflected on the boundary between the two interfaces. There are similarities between sound waves and light waves. When sound waves are incident obliquely when they contact the interface of an object, the incident angle will be equal to the reflection angle. When the reflection surface is flat and the scale is larger, it is like a mirror reflection effect, specular reflections will occur [1]. If the reflecting surface has a concave-convex texture or decoration, and the wavelength of a certain frequency band is equivalent, the intensity of the reflected sound will be reduced, and the reflected energy will be scattered at various angles, which is called diffuse or diffuse reflections [2, 3]. In addition to the natural physical characteristics of the sounds mentioned above, the use of Sound reinforcement can compensate for the limitations of natural conditions, especially in large hall spaces. Through the use of acoustic equipment, it can provide sufficient volume, adjust the characteristics of the sound and the balance of the vocal part during the performance, and can record or reproduce. For general performance venues, for all audience seats, the volume of the sound reinforcement system must provide more than 85 dB, and the volume of rock performance venues must reach as high as 110 dB. In addition to providing sufficient volume, the sound clarity of the system may also be discussed, the range of output frequency meets the requirements of a high standard. The equipment system consists of sound receiving equipment, reproduction and recording equipment, processing and control equipment, etc., from traditional analog signals to digital signals, the integration of signal workstation systems has become the trend of sound field evaluation and application implement. In terms of the acoustic characteristics of interior space, the radiation of sound in the indoor space will cause a series of reflections. After a distance from the sound source, the sound volume will be mainly controlled by the reflected sound. Apart from the outside distance, the sound volume will not decrease significantly. The scale of the space is also related to the characteristics of the sound distribution. The smaller the interior space and the higher the surface reflection intensity, the greater the volume of sound. An impulse response is an acoustic effect recorded at a certain measurement point (Receiver) in a room, corresponding to one or more sound source points (Source) with a sound producer. An impulse response is a communication tool for acoustic consultants and architects. It can be used to understand the detailed relationship between subsequent reflections (such as early reflections) and direct sounds. It also includes late energy, such as reverberation energy. This response records the arrival time and sound energy of direct sound and various subsequent reflections [4]. In the past fifty years, in the physical study of natural sound in halls, acousticians have successively proposed many acoustic measures (Acoustical measures) to represent several important subjective acoustic elements. Most of these indicators are evaluated by listening to music. The main physical quantities include Reverberation Time (RT), when the sound stops, due to the existence of reflection, the sound does not disappear immediately but gradually decays. This process is called reverberation, and the corresponding physical index is called reverberation time (RT). The phenomenon generally refers to the time duration after attenuation of 60 decibels (dB). In general interior, the reverberation or clarity can be considered as two sides of the condition, that is, when the reverberation is increased, the clarity is decreased. Therefore, considering the two factors of space and time, the performance space required for a specific performance object has a certain scale and material characteristics. Generally, the small space requires high definition, and the reverberation time is short. The planning of the reverberation time (RT) value is recommended to be about (0.6–1 s) according to the space size. Acoustical indices, such as RT30, C80, D50, Ts and EDT, are derived from the impulse response which is based on the International Standard ISO 3382 (Bradley 2004) [5]. Through the distribution of sound absorption and diffusion materials in the indoor space, the initial reflected energy is effectively radiated to the seat. The ideal indoor space is a moderate size of 16.5–49.5 square meters. If the space is less than 13 square meters, there may not be enough space for sound reflection, and the sound easily floods the overall environment, covering too much area, affecting the clarity of the sound. The larger the space volume or the higher the reflection intensity of the surface material, the longer the reverberation time. The size and shape of an interior environment will have a great impact on the sound equipment of the device. The shape and size of the space will affect the path of sound propagation in the space, thus causing a difference in a person’s viewing experience. The interior space is between two planes. As a result, sound waves are constantly reflected to form standing waves. Therefore, in spatial planning, eliminate the concentrated sound wave path and let the energy of the sound be evenly distributed in the space. In the interior where the spatial unit is located, it is best to stay away from the environment that may cause noise, such as the side of the road or the adjacent space that generates noise. If it can be an independent enclosed space, it will be more effective in blocking environmental noise and improve the space. Sound quality, play the effectiveness of film and television listening equipment.

2 Visualization of Sound Distribution

In addition to the design of the building space, the sound energy distribution has an impact on the sound filed. In order to further confirm the morphology of indoor sound field performance planning goals and the independence and correlation of acoustic parameters, the computer simulation evaluation technology includes several item-oriented discussions, including sound energy of diffused field to estimate the sound insulation performance of indoor structures evaluation, and finally, after the completion of the verification measurement, an objective test is performed to record the physical performance of real-time condition and explore the corresponding relationship with the objective physical measurement of the room. In this phased study, computer simulation is used to predict and evaluate the sound field model and the sound insulation performance of indoor structures. In the 1960s, Shroeder [6] introduced the basic principles of computer simulation to indoor acoustics. Krotstad [7] first published a paper on computer simulation of indoor sound fields. With the continuous advancement of software and hardware technology, the computer simulation software for hall sound quality has matured and is widely used in hall research on sound quality design and evaluation of sound field characteristics. The computer simulation of the indoor sound field simulates the propagation law of sound waves in the room by establishing a mathematical model of the actual hall according to the geometric acoustic method. The acoustic simulation software uses the Lamber scattering algorithm, and the calculation results are closer to the measured values. Due to the establishment and modification of the digital model and the establishment of the material database, the data environment of these parameters can be used to view the sound quality environment with high accuracy. The relative software was be presented, it can reduce the time needed for the creation of noise contour maps considerably. The development of a fit for purpose software for mapping contours based on measurements. Scanned maps and CAD drawings can be used as backgrounds for future evaluation. The actual measurement is used to draw the sound energy distribution map, and the NoiseAtWork software is used to analyze and draw the distribution curve. The results can be used to establish the optimization plan for the overall distribution of the sound field. Individual environmental factors can be used to verify and hypothesize to construct The model, through the implementation of measurement correspondence, further draws sound pressure level images and verifies sound field models, predicts future scenes and benchmarks for subjective evaluation, and then takes measures. Using the computer simulation of the sound field environment results, the calculation method to perform grid calculations, draw the sound energy distribution curve diagram, which has an intuitive trend and visual representation, and can evaluate the sound field in which it is located under different conditions surroundings. The simulation results provide a lot of information, including the location and strength of sound energy. In some cases, this method has the function of trend prediction, especially under stable sound sources, such as fixed noise sources (fixed mechanical sound), and multiple sound source are conducted for the measurements (See in Fig. 1.).

Fig. 1.
figure 1

Multiple standing sound source are conducted for the simulation and calculation with on-site sound energy distribution

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The mapping contours presentation is based on measurement results with the equivalent average volume LAeq (dB) as the evaluation index and the A-weighted noise intermittently exposed in a certain period of time in the selected position in the sound field are averaged by the energy. The parameter index formula is shown in Eq. 1.

$$ LAeq = 10 \,log\frac{1}{T}\int_{t}^{t + T} {\left( {\frac{Pt}{P0}} \right)^{2} dt} $$
(1)
LAeq::

A-weighted average energy level dB (A) in period time;

T::

measurement time in seconds;

Pt::

measure sound pressure in Pa;

P0::

reference sound pressure, based on 20 Î¼Pa

For different sound sources, measures to reduce sound energy can also be plotted and sorted according to the size of the sound energy results. NoiseAtWork software is used to simulate and draw the sound energy distribution curve to establish the overall distribution of the sound field and the overall distribution profile. Individual environmental factors can be used to verify and hypothesize to build a model. Through the implementation of measurement correspondence, the sound pressure level image and Validate the sound field model, predict future scenarios and explore the impact of sound source energy, and then take corresponding measures. Results can be discussed and evaluated simultaneously (See in Fig. 2).

Fig. 2.
figure 2

Results of calculation within the occupational noise sector and present the visualization of mapping contour.

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3 Calculation of Sound Insulation for Building Element

Sound insulation performance of building structures through construction system require regulations to reduce noise interference between different units. There are many reasons for the indoor noise environment of the building, including the airborne noise of neighbors and outdoors. Noise is transmitted into the room through building doors and windows, walls and floors, and the vibration of equipment inside the building and the indoor activities of residents constitute in noise environment, which has become one of the causes that bother and affect their quality of life. There are existing regulations on sound insulation and the goal is to strengthen the building’s sound insulation structure to reduce noise interference between residential occupants and improve the quality of the home audio environment. Air sound insulation design and floor impact sound insulation design have their application scope. Domestic residential common 150 mm thick RC wall surface cement mortar painted individual household walls, the site sound insulation level can reach more than 50 dB, with good sound insulation performance is equivalent to the requirements of foreign sound insulation benchmarks. The analysis results have the same trend, with high correlation, which shows that the results of the individual household wall test in this study are really valid. In addition, RC bare floor slabs commonly used in domestic housing, and effective countermeasures against impact sounds, have become a source of distressing noise for collective residential residents. As long as the mass per unit area (m) and the Modulus of Elasticity (E) of the panel are known, the sound transmission through a single-layer plate can be approximated to a good accuracy. At low and mid frequency bands, the acoustic transmission loss (TL) is calculated according to the mass law [8, 9]. The prediction formula is shown in Eq. 2.

$$ {\text{TL }} = \, 20\,{ \log }\left( {\text{mf}} \right) \, {-} \, 48{\text{ dB}} $$
(2)

At high frequencies, the coincidence effect weakens the acoustic transmission, and the transmission loss is given by Eq. 3

$$ {\text{TL }} = \, 20\,{ \log }\left( {\text{mf}} \right) \, + \, 10\,{ \log }\left( {\text{f/fc}} \right) - 44{\text{ dB}} $$
(3)

Another simulation of program that can estimate the sound insulation ability of partition walls, floors, ceilings and windows. It can make a more accurate estimation of the sound transmission loss of 1/3 octave and the weighted sound insulation (STC or Rw) which can be used for noise evaluation. It takes account of finite size effects which are very important when predicting small samples such as windows and also for normal elements at low frequencies. The low-frequency sound transmission effect of very important small-sized building structures is considered in the calculation of sound insulation, and it is applied to the estimation of small-sized building structures such as windows and ordinary building structures. As with other estimation tools, simulation is not a substitute for actual measurement. However, according to the comparison with the test data derived from the database, for most building structures and elements, the difference can be within 3 decibels. The materials databases can be filtered to include or exclude materials from most of the countries and it is adapted to most regions in the world. The databases are updated regularly and feedback from users is always welcome to extend and improve the material selections. For the example of calculation for the prediction transmission loss of double panel systems may refer to in 4 different frequency regions. At low frequencies the transmission loss is determined primarily by the mass law. The mass-air-mass resonance frequency of the partition (fo) determined by the mass of the panels and the air gap, the TL increases at 18 dB/octave as the two sides become decoupled. The other region the cavity width becomes comparable to a wavelength at frequency fL the cavity modes couple the panels together and the TL increases at 12 dB/octave. The last concerns is focused on the solid connections act as sound bridges between the two panels and the TL is limited to a constant amount above the mass law, and increases at only 6 dB/octave [10]. The results of double layer of lightly structure for sound insulation calculation as shown in Table 1.

Table 1. The results of insulation calculation for double layer of lightly structure
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4 On-Site Measurement

Taking into account the current indoor environment and sound field environment quality, conduct a current environmental assessment. The measurement results will provide a basis for the design decision of the construction team. Based on the data measured and analyzed at the site, a preliminary improvement proposal and performance proposal are proposed. With reference to the ISO140-3 the difference of SPL field measurement method, the spatial sound pressure level difference is calculated by Eq. 4. In addition, the correction formula of the opening area is included in Eq. 5.

$$ TL = L_{1} - L_{2} $$
(4)
$$ R^{{\prime }} w = TL + 10\,log \, S/A $$
(5)
TL::

Sound transmission Loss (dB).

L1::

Averaged SPL at source room (dB).

L2::

Averaged SPL at receive room (dB).

S::

Area of test species (m2).

A::

Absorption coefficient at receive room (dB)

The acoustic parameters in the physical quantities of the indoor sound field are mainly described in terms of Reverberation Time (RT). After the sound energy stops, due to the presence of reflections, the sound does not disappear immediately, but gradually decays. This process is called reverberation, and the corresponding physical index is called reverberation time (RT) as previous mentioned. Evaluation of sound insulation performance of building elements (such as walls, doors or windows) are based on ISO140-3 and ISO717-1 measurement methods to regulate and evaluate performance. Insulation performance standards for most typical building component sound need to be between Rw 45–50 dB, and more than 50 dB is a high-performance sound insulation construction. Rw is a parameter value measured under careful settings and conditions in the laboratory. Under field conditions, it is represented by R′w. For example, the sound transmission problems such as the socket that the opening of the partition wall intersects with the slot, and other lateral sound transmission channels. The noise generated by structural vibration through the structure of the wall must be solved and concerned. According to the ISO standard, the sound insulation performance of the building in the indoor space is evaluated (the openings are all closed). The test frequency band range is 1/1 times the octave 100 Hz to 3150 Hz. In addition to the indoor sound insulation performance test, the volume of the corridor affects the adjacent indoor space. Finally, after clarifying the sound insulation performance, the indoor and speech intelligibility will be significantly improved. The detailed description of the on-site measurements and the corresponding evaluated spaces are described in Table 2. The field measurement results for test specie are listed in Table 3 and 4 according to the performance of the ISO717-1 specification.

Table 2. The detailed description of the on-site measurements and the corresponding evaluated spaces are listed
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Table 3. Acoustical parameters with on-site measurement at receiving room are listed
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Table 4. The field measurement results of specification.are listed according to the sound insulation performance of the ISO717-1
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5 Discussion

In interior design research, the perception of space and related senses is very important. In addition to visual aesthetic performance, the sound effects of musical instruments, sounds and relative sounds are just as important as visual perception. During the acoustic design of the room, the physical properties of the sound insulation were proposed. The design method for the characteristics of space shape, room volume, materials and detailed decoration is to predict the sound performance requirements above design concerns. The measurement of sound insulation is mainly based on the impulse response, which represents the physical reaction between a point in space and the sound source. In the performance design process, different evaluation of sound insulation techniques can be used to obtain the impulse response as the basis for sound field evaluation. This research explains the correspondence between interior design and sound insulation performance for topics such as sound transmission loss theory, computer simulation, and on-site measurement techniques. Some preliminary results are abstracted as followed:

  1. (1)

    Individual environmental factor can be used to verify and hypothesize to build a model by the simulation and easy to demonstrate the calculation of results with mapping contour for further prediction.

  2. (2)

    Sound insulation performance of building structures through construction system require regulations by the software to reduce noise interference before the approaches of detailing design.

  3. (3)

    The on-site measurement verification can be obtained through the analysis of the instrument and digital workstation. After analysis by the digital signal workstation, each parameter must be entered into the simulation software for data analysis and systematically organized.