Category: Asia Noise News

Categories
Asia Noise News Building Accoustics Noise and Vibration Product News

The Nano-guitar String that Plays Itself

Scientists at Lancaster University and the University of Oxford have created a nano-electronic circuit which vibrates without any external force.

Using a tiny suspended wire, resembling a vibrating guitar string, their experiment shows how a simple nano-device can generate motion directly from an electrical current.

To create the device, the researchers took a carbon nanotube, which is wire with a diameter of about 3 nanometers, roughly 100,000 times thinner than a guitar string. They mounted it on metal supports at each end, and then cooled it to a temperature of 0.02 degrees above absolute zero. The central part of the wire was free to vibrate, which the researchers could detect by passing a current through it and measuring a change in electrical resistance.

Just as a guitar string vibrates when it is plucked, the wire vibrates when it is forced into motion by an oscillating voltage. This was exactly as the researchers expected.

The surprise came when they repeated the experiment without the forcing voltage. Under the right conditions, the wire oscillated of its own accord.

The nano-guitar string was playing itself.

Lead researcher Dr Edward Laird of Lancaster University said: “It took us a while to work out what was causing the vibrations, but we eventually understood. In such a tiny device, it is important that an electrical current consists of individual electrons. The electrons hop one by one onto the wire, each giving it a small push. Usually these pushes are random, but we realized that when you control the parameters just right, they will synchronize and generate an oscillation.”

So what note does the nano-guitar play?

“The nanotube is far thinner than a guitar string, so it oscillates at much higher frequency — well into the ultrasound range so no human would be able to hear it.

“However, we can still assign it a note. Its frequency is 231 million hertz, which means it’s an A string, pitched 21 octaves above standard tuning.”

The nano-oscillator could be used to amplify tiny forces, such as in novel microscopes, or to measure the viscosity of exotic quantum fluids. These experiments will be pursued in a new laboratory that Dr Laird is setting up in the Physics Department at Lancaster, supported by a €2.7M grant from the European Union.

Credit: https://www.lancaster.ac.uk/news/the-nano-guitar-string-that-plays-itself

Written by: Phawin Phanudom

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
Asia Noise News

Noise, Nuisance or Danger

As an introduction to this question some basic facts about noise.

Basic noise facts

Noise is typically defined as ‘unwanted sound’. The unit for sound is the Decibel which is a value calculated with logarithms from the pressure to get a scale from 0 to 120 dB where 0 dB is the hearing threshold for a young person with healthy hearing and 120 dB is the pain threshold.

We can state that noise is a type of energy created by vibrations. When an object vibrates it causes moment in air particles. The particles will bump into each other and will generate sound waves, they are ongoing until they run out of energy.

High and low tones are perceived by our hearing due to fast and slow vibrations.

Sound needs a medium to travel and the speed of sound is around 340 meter per second. Examples of typical noise levels:

Due to the nature of the calculation of Decibels we cannot just add them together.

Examples:

3 dB + 3 dB = 6 dB

But…..

10 dB + 10 dB is not 20 dB but 13 dB

The Decibel (sound pressure level) for sound in air is relative to 20 micro pascals (μPa) = 2×10−5 Pa, the quietest sound a human can hear.

The human hearing system

The human hearing system is capable of hearing sounds between 20 Hz and 20000 Hz. Below 20 Hz is called infra sound and above 20000 Hz is called ultrasounds. Both infra- and ultrasound is not audible for us. Elephants however can hear frequencies as low as 14 Hz and bats can hear frequencies up to 80000 Hz.

A special noise weighting for the human perception has been introduced in the 1930’s and called the A-weighted Decibel, dB(A). This was introduced to align the noise levels with the sensitivity and physical shape of the human hearing system.

Basic human hearing system

When sound waves enter the ear, they travel up the ear canal and hit the ear drum, the ear drum will vibrate and the three smallest bones in the human body will transfer these vibrations to the fluid in our inner ear’s sensory organ the cochlea. The sensory hair cells will vibrate which will send nerve impulses to the brain, the brain will translate these impulses for us and we perceive sound!

Dangers of noise

Noise from certain music can be a very pleasurable sound for one person and a horrific noise for another. From this fact we can see that noise is not only an absolute value but also strongly depending on the receiver’s mindset.

However, there are some clear absolute values concerning the danger levels of noise.

  • Generally accepted as safe is spending 8 hours per day in an environment not exceeding 80 dB(A)
  • NOT safe would be to spend 1 hour in a disco with levels at 100 dB(A) which are easily exceed nowadays

Apart from the obvious hearing loss there are many other issues that can arise from exposure to (too) high noise levels such as:

  • Hypertension
  • Heart disease
  • Annoyance – stress
  • Immune system – psychosomatic

The positive side to remember is that Noise Induced hearing loss is 100% preventable!!

Worldwide solutions

Governments (especially in Europe) know the actual cost of high noise exposure and they concluded that protecting their citizens from high noise exposure (during working hours, recreation as well as during sleep) is far more effective than dealing with the costs of citizens enduring high noise related illnesses, demotivation, sleep disturbance etc.

They are investing in quiet schools (optimal learning environment), quiet hospitals (patients recover a lot faster in quiet wards), implement city planning to create quite zones.

Of course, they also have strong noise regulations that are being enforced.

Acoustical societies worldwide help to create awareness and leverage noise legislations with governments.

Noise in Asia

I have been living in Asia for the last 15 years and of course I noticed it’s noisy. Noise regulations (if exist at all) are very lenient and mostly not enforced. I’m very happy to see that Acoustical Societies are coming up in Asian countries and can convince governments to invest in setting up proper noise regulations and enforcing them. I’m very happy to be able to contribute to a quieter world by creating more awareness for the dangers of noise!

Thailand