Author: Richy

Categories
Asia Noise News

A Review of Acoustics in the Hospitality Industry: A Subjective and Objective Analysis

Many bars, cafés, and restaurants have been built in Asia, that is one of the indications that the hospitality industry is moving forward. Our need for entertainment, refreshing our mood, and communication with friends, family members, or business clients are reasons why we need the hospitality Industry such as; bars, cafés, and restaurants as a place for us to do that kind of activities. Comfortableness becomes a top priority to determine if a bar, café, or restaurant is a pleasant place to be or not. One of the criteria is comfortableness in acoustics aspect, how easy the customers can have a conversation, a relaxed ambience and quietness. In Asia, especially in developing countries, acoustic comfort in bars, cafes or restaurants is not yet a major concern, even though the effect will be huge for their visitors’ comfort. One example of the impact of bad acoustic design on a cafe or restaurant is the difficulty of communicating, even though one of the things that visitors want to do is chat with family, friends or work partners. This situation will give a bad impression of the café or restaurant and reduce the number of visitors to the café or restaurant.

In this article, the author will discuss the research conducted by Lauren H. Christie and J. R. H. Bell Booth – Victoria University of Wellington. This study is titled “Acoustics in the Hospitality Industry: A Subjective and Objective Analysis” this research examining several Bars, Cafes, and Restaurants around Wellington CBD related to acoustic comfort based on objective and subjective parameters which are then compared to AS / NZA 2107:2000.

The results of the research at the cafés, bars and restaurants in Wellington CBD found that the average noise level that occurred was 80 dBA and could even reach as high as 110 dBA. If it is compared with the level of sensitivity of human hearing to speech that only ranges from 48 dBA to 72 dBA [AS / NZA 2107: 2000] this very much exceeds the limit. The NC (Noise Criteria) suggested in this study are:

  • Bar : 45 – 50 dBA
  • Café : 45 – 50 dBA
  • Restaurant : 35 – 50 dBA

As reviewed earlier, research conducted by Lauren H. Christie and J. R. H. Bell Booth takes 2 parameters, they are subjective and objective parameters. Subjective consists of a Survey Questionnaire that is spread to visitors about the information conveyed, the ability to listen, the dominant difficulties that occur, and the desired ideal conditions. This is called subjective because it is qualitative and is adjusted to personal tendencies. The second parameter is Objective, consisting of measured parameters such as BN (Background Noise), Leq, RT (Reverberation Time), STI (Normal, Rise, Loud, Shout).

BN is measured by measuring the level of sound pressure in conditions without visitors, the use is as an acoustic base value without additional noise. Leq is the average noise over a period of time, this is done as sample information on the noise value of the place. RT or Reverberation Time is the time required for the sound to decay as much as 60 dB, this parameter is used as a base for evaluating the comfort of the conversation or music in a room, RT that is too high will make someone difficult to communicate because the sound will be reflected and reduce the clarity of the conversation. STI or Speech Transmission Index is a parameter to assess the level of comfort in terms of listening to speech or conversation, the value ranges from 0 to 1 with a value of 1 is perfect or very clear STI.

The age range of visitors looks similar if evaluated based on the survey, most visitors in a bar are under 25 years old, while in the cafés and restaurants most visitors are in the range of 25 – 35 years old. Based on the survey results, the need for acoustic quality related to the highest conversations is in restaurants, followed by cafés and bars. This is very clear because the restaurant visitors have a lot of verbal interaction or direct communication when eating. At the café, there tends to be less communication and more listening to the ambiance and relaxing music with less communication if we compare it with a restaurant. The last ranked is the bar, visitors will only listen to music to arouse their mood and rarely communicate. The highest source of noise comes from other visitors’ communications, which is followed by the sound of music and kitchen equipment.

Acoustic comfort based on survey results or subjective parameters are as follows:

Restaurant

  • Restaurants are expected to have a low Background Noise and a good STI, but the actual situation in most of the restaurants researched is far from that.
  • Privacy is a very important variable in a restaurant.
  • The clarity in terms of speech is low.
  • Visitors in the restaurants are very difficult to be heard/understood when they are talking.

Bars

  • Bar customers said that a bar is more acceptable to noise than a cafe or restaurant.
  • Even though it is difficult to communicate, the bar can be accepted by visitors.
  • Bar customers need more effort to communicate.
  • The type of people who visit the bar are people who are accustomed to noisy environments.

Café

  • People who often visit a café find it easy to communicate at the café.
  • Clarity of speech is seen as a more important factor than the visitor’s environment.
  • Café is also rated as the most unacceptable environment from this acoustic-related survey.

Based on objective parameters, the results are: BN (Background Noise is in the range of 34 dBA (Leq) to 81 dBA (Leq), where 60% of the data is worth more than 50 dBA (Maximum level in AS / NZA 2107: 2000). After measuring with visitors inside, the level of the noise reaches 25dB beyond the maximum visited level, but when compared to the OSH recommendation safety limit, 85 dBA (Leq), the value is still below the threshold (the highest level of measurement is 81 dBA).

For the RT value, both the bars, cafés and restaurants are within the standard of <1.0 S. STI rating is found to be very diverse, but from the use of the 4 types of sound that are normal, raised, loud, and shout the same pattern is obtained, the higher the sound level, the better STI. From this research, we know that there are differences in preferences of acoustic comfort factors in bars, cafes, and restaurants. The difference in preferences is due to differences in the main functions of each hospitality industry. At the restaurant, visitors expect to be able to communicate well in one scope of the table and maintained privacy from the scope of another table. At the café, the need for tranquility is the main thing and the need for communication is not as high as the restaurant. At the bar, the main needs of visitors are listening to music and not too concerned about communication difficulties.

So, has your hospitality industry considered acoustic comfort? It’s a very important aspect to keep visitors coming back to your venue!

Written by:

Betabayu Santika

Acoustic Design Engineer

Geonoise Indonesia

Beta@geonoise.asia

Source:

AS/NZS 2107 (2000). Acoustics – Recommended design sound levels and reverberation times for building

interiors. Australian/New Zealand Standards: Sydney/Wellington.

Bell-Booth, J. R.H. (2004). Methodology Research.

Christie, L. H. (2004). Acoustical Comfort: Research Design into Measuring Restaurants and

Bars Acoustic Environments.

Christie, L. H. & Bell-Booth, J. R.H. – Acoustics in the Hospitality Industry: A Subjective and Objective Analysis

Categories
Asia Noise News

Calibration

Sound measurement is one of the measurements which is considered to be important in a lot of different industries. For example, automotive, manufacture, HSE, research and so on. One of the aspect that is important for all measurements are its calibration. Calibration is a process of documenting and adjusting the reading of measurement instruments with a traceable reference. 

The frequency range of acoustic measurement in air is wide, from infrasound to ultrasound. From tenth hertz to 200 kHz. It is measured in a wide range of dynamic range too, from 20 micropascal to 20 kilopascal. Therefore, to be able to conduct these measurements in a wide range of frequency and dynamic, different kinds of microphone is used.

Most measurement microphones and reference microphones is condenser microphone. This type of microphone is widely chosen because of its flat frequency response and a good mechanical stability. The standard used for measurement microphone is IEC61094-4 which is called working standard microphones, abbreviated WS. WS microphones are categorized into 3 types based on its diameter which are 23.77 mm, 12.7 mm and 6.35 mm. These three microphones are called WS1, WS2 and WS3 respectively.

Another standard is used for Laboratory Standard Microphone, abbreviated LS, which is IEC61094-1. Similarly to WS, LS can be categorized by its diameter, which are LS1 with 23.77 mm and LS2 with 12.7 mm diameter. LS microphone is designed so that it can be fitted into calibration coupler and is normally used by national metrology institute as a national reference in a country. Both of the standards mentioned above specify dimension, sensitivity, frequency response, acoustic impedance, dynamic range, ambient influence and stability.

Condenser microphone is a reciprocal transducer. This microphone can work as a microphone by converting acoustic signal into electric, as well as working as a sound source by converting electrical input into acoustic output. This is why condenser microphones can be calibrated by a calibration method called reciprocity.

Before we discuss further about the calibration method, it is useful to discuss about sound field and the type of microphone used to measure in such fields. There are three types of sound field in general. In a cavity which dimension is smaller than a quarter of the measured wavelength, the soiund field is called pressure-field. This field happens in a calibration coupler for microphone calibration, telephone and hearing aids, for example. Sound field in an anechoic chamber or outdoor where sound can propagate without obstacles is called free-field. While sound field in a reflective room is called diffuse-field. 

All types of microphones can influence the sound field which is being measured, including condenser microphone. Microphones that are used in cavities should have a stiff diaphragm, or in another word has a high acoustic impedance. For free-field condition, microphones that are chosen ideally has a diameter less than 5-7% from the wavelength of the sound being measured. In practice, this rarely happens, so that the influence has to be taken into account in the measurement results. Similar situation happens in diffuse-field, although the influence is relatively smaller.

Note that the influence in the free-field and diffuse-field depends only on the dimension of the microphone’s body. Because of this reason, the influence only have to be measured once for the same microphone model. After the influence is defined, it can be applied to all the same microphone of the same model. 

Let’s go back to reciprocity calibration. This method was invented in the 1940s. This method has been developed and standardised which makes the method one of the most widely used calibration techniques to determine microphone’s response in pressure-field and free-field. The calibration method is based on transfer function of two microphones which are coupled as microphone and sound source.

The two microphones are coupled in a well-defined acoustic environment. The transfer function which is the ratio between output voltage of the sensor and input current of the source is measured. This ratio is called electrical transfer impedance (Ze). Furthermore, by knowing the acoustic transfer impedance (Za), the product of the sensitivity of the two microphones can be defined by this equation.

Where M1 and M2 is the sensitivity of microphone 1 and microphone 2, Ze/Za is the ratio between electric and acoustic transfer impedance.

By using three microphones (1,2,3) and defining three impedance ratio equations (A,B,C) for three possible combinations (1-2, 1-3, 2-3), the sensitivity of three microphones can be calculated by solving these three equations.

Some national metrology institutes are doing reciprocity calibration for laboratory standard microphones. The frequency ranges from 20Hz to 10kHz for LS1 and 20Hz to 20kHz for LS2. Some of the institutes has experience in calibrating lower or higher frequency range.

Categories
Asia Noise News

Profound November News

SIT-mounted sensor for Wave Hammer

The Profound mounted accelerometer for the SIT-series has been custom-designed for high performance integrity testing of installed foundation piles. Especially for large diameter bored piles this sensor enables optimal circumstances to perform the measurement.

Advanced design and application
The SIT-mounted sensor is an alternative to the hand-held sensor whereby the sensor is fixed on the pile head using a separate mounting plate. One or more mounting plates can be mounted on the pile head in advance of the actual measurement. During the measurement the stiff connection between the mounted sensor and pile head ensures optimal high-quality measurement results, asthe mounted sensor registers exceptionally well the response to the hammer blow. Thus providing users with accurate information about the pile shaft and possible defects.
The mounted accelerometer is ideal to be used in combination with the Wave Hammer range for large diameter piles.

News from Soil Instruments Ltd.: GEOSmart

GEOSmart is an in-place inclinometer consisting of closely spaced MEMS 0.5 metres apart. The sensors are mounted on stainless steel tubing with a single cable running the length of the string which reduces the number of cables protruding from the top of the borehole. GEOSmart is installed in either PVC Schedule 40 or 70mm casing and is used to monitor displacement in geotechnical applications including diaphragm walls, embankments, retaining walls, landslides and potential slope failures. Due to its lightweight robust construction with joints capable of bending up to 90o, GEOSmart is conveniently transported to site and can be installed by one site technician. At the end of the project GEOSmart can be removed and reused whereby the length of the string can be easily adapted.

New features vibramonitoring.com

With the new features on vibramonitoring.com we have created a new datasheet. Please contact us for the new datasheet.

Partnership VDV : online monitoring

We are proud to announce that from now on we have entered into a partnership with Vista Data Vision (VDV). VDV supplies leading software for the visualisation of data for geotechnical monitoring projects.

The VDV platform offers extensive and straightforward options presenting all measurement data of the different instrumentation in one project to your clients. The platform offers numerous options for setting threshold values, alarms, user accounts and for combining information from various equipment such as: VIBRA systems, Robotic Total Stations, IPI sensors, noise monitoring systems, air quality monitors. It is also possible to integrate webcams.
VDV Burst Data allows to import high speed dynamic data such as from instruments made by Profound. The data is imported into the VDV database and can then be viewed with all other data types already supported by VDV.

Exhibitions

In October we attended 2 Dutch conferences: the 23rd GTL for Sound, Vibration and Air Quality in Hoevelaken and the Geotechnical conference in Breda. The reactions to all the new products like the Wave Hammer, mounted sensor, the partnership with VDV and the early impressions of the VIBRA-r were very positive.
Our special guest Chris Wembridge of Soil Instruments Ltd. demonstrated the GEOSmart system himself at the Geotechnical conference.

Categories
Building Accoustics

Researchers Develop ‘Acoustic Metamaterial’

Boston University researchers, Xin Zhang, a professor at the College of Engineering, and Reza Ghaffarivardavagh, a Ph.D. student in the Department of Mechanical Engineering, released a paper in Physical Review B demonstrating it’s possible to silence noise using an open, ring-like structure, created to mathematically perfect specifications, for cutting out sounds while maintaining airflow.

They calculated the dimensions and specifications that the metamaterial would need to have in order to interfere with the transmitted sound waves, preventing sound—but not air—from being radiated through the open structure. The basic premise is that the metamaterial needs to be shaped in such a way that it sends incoming sounds back to where they came from, they say.

As a test case, they decided to create a structure that could silence sound from a loudspeaker. Based on their calculations, they modeled the physical dimensions that would most effectively silence noises. Bringing those models to life, they used 3-D printing to materialize an open, noise-canceling structure made of plastic.

Trying it out in the lab, the researchers sealed the loudspeaker into one end of a PVC pipe. On the other end, the tailor-made acoustic metamaterial was fastened into the opening. With the hit of the play button, the experimental loudspeaker set-up came oh-so-quietly to life in the lab. Standing in the room, based on your sense of hearing alone, you’d never know that the loudspeaker was blasting an irritatingly high-pitched note. If, however, you peered into the PVC pipe, you would see the loudspeaker’s subwoofers thrumming away.

The metamaterial, ringing around the internal perimeter of the pipe’s mouth, worked like a mute button incarnate until the moment when Ghaffarivardavagh reached down and pulled it free. The lab suddenly echoed with the screeching of the loudspeaker’s tune.

How acoustic metamaterial works – Geonoise Instruments
How acoustic metamaterial works – Geonoise Instruments

Now that their prototype has proved so effective, the researchers have some big ideas about how their acoustic-silencing metamaterial could go to work making the real world quieter.

Closer to home—or the office—fans and HVAC systems could benefit from acoustic metamaterials that render them silent yet still enable hot or cold air to be circulated unencumbered throughout a building.

Ghaffarivardavagh and Zhang also point to the unsightliness of the sound barriers used today to reduce noise pollution from traffic and see room for an aesthetic upgrade. “Our structure is super lightweight, open, and beautiful. Each piece could be used as a tile or brick to scale up and build a sound-canceling, permeable wall,” they say.

The shape of acoustic-silencing metamaterials, based on their method, is also completely customizable, Ghaffarivardavagh says. The outer part doesn’t need to be a round ring shape in order to function.

“We can design the outer shape as a cube or hexagon, anything really,” he says. “When we want to create a wall, we will go to a hexagonal shape” that can fit together like an open-air honeycomb structure.

Such walls could help contain many types of noises. Even those from the intense vibrations of an MRI machine, Zhang says.

According to Stephan Anderson, a professor of radiology at BU School of Medicine and a coauthor of the study, the acoustic metamaterial could potentially be scaled “to fit inside the central bore of an MRI machine,” shielding patients from the sound during the imaging process.

Zhang says the possibilities are endless, since the noise mitigation method can be customized to suit nearly any environment: “The idea is that we can now mathematically design an object that can block the sounds of anything”.

Source:

https://phys.org/news/2019-03-acoustic-metamaterial-cancels.html

Categories
Asia Noise News Building Accoustics

Noise and Vibration Monitoring for Construction Sites

In a densely populated city like Bangkok, most of the construction projects are surrounded by condominiums, offices or residential areas. The construction sites must control the noise and vibration that may affect the surroundings. Construction sites need to control the noise and vibration levels that they produce following the EIA standard.

To manage this, noise and vibration instruments are installed which automatically will send alarms to the construction company if the thresholds are exceeded.

Noise Monitoring Station

Sound level meter class 2 according to IEC61672-1 standard which can collect the data of SPL, LEQ and LMAX. These instruments are calibrated before they are installed at a construction site. The system has a LED display and warning light when noise levels in the site are over a trigger level, which is referred to in the standards for maximum sound levels around construction sites.

According to the announcement of National Environment Board no.15 BE.2540 (1997) in the topic of “Standard loudness”, the average sound 24 hour must not exceed 70 dBA and the maximum peak level must not exceed 115 dBA.

Sound level meter are designed to be used outdoors and an additional LED display was added by Geonoise which is a professional sound and vibration company. Sound level meter with LED display also can analyse the loudness in percentile (Statistical,Ln) or analyse the frequencies in 1/1 and 1/3 octave bands. In addition to storing vibration data, you can also create level notifications in Alarm Alert format before vibration levels exceed the standard value for monitoring the activities being performed.

Vibration Monitoring

In the construction industry, transportation Industry and most large industries vibrations will occur.
High vibration levels will cause structural damage to buildings, bridges, structures as well as nuisance or health risks to occupants in exposed (residential) buildings.

Therefore, it is necessary to comply with the standard of vibration in a building according to the Announcement of the National Environment Board Announcement No. 37, BE 2553 (2010) Re: Determination of Standard Vibration to Prevent Impact on Buildings and the measuring instruments need to comply with DIN45699-1.

At construction projects in Bangkok, most cause a lot of unwanted noise and vibrations. Vibration caused by construction projects are caused by piling work as well as the increased traffic of large trucks that enter and exit the construction site. To prevent that vibration levels will be exceeded, a vibration monitoring system will have to be installed.

The Announcement of the National Environment Board No. 37, BE 2553 Vibration standards to prevent impacts on buildings is the main regulation to comply with for construction sites in Thailand. The vibration standards are derived from DIN 4150-3 whereas buildings are classified into 3 types.

Building types according to DIN 4150-3:

  • Type 1 buildings such as commercial buildings, public buildings, large buildings, etc.
  • Type 2 buildings such as residential buildings, dormitories, hospitals, educational institutions, etc.
  • Type 3 buildings, such as archaeological sites or buildings that cultural values but not strong, etc.

In addition to storing vibration data, you can also create level notifications in Alarm Alert format before vibration level exceed the standard value for monitoring the activities being performed.

Thailand