Categories
Asia Noise News Building Accoustics

Noise in HVAC System; What, Where and How Noise comes from?

One of the things that becomes an unpredictable issue of a building, especially with a centralized air conditioning system, is the noise it creates. Calculating noise from every part of the HVAC system is needed to avoid unwanted noises in adjacent rooms.

What do we need to know to avoid noise from the HVAC system?

Are there simple steps to avoid it?

In this article, we will discuss about the noise that occurs in the HVAC system and how to avoid it.

Every sound that is heard can usually be identified through its frequency range. In relation to frequency range, noise that occurs related to the HVAC system is divided into 3 categories within the frequency range:

  • Low Frequency

Fan Noise, it generally produces sound from 125 Hz to 500 Hz octave frequency bands. Variable Air Volume (VAV) boxes noise is usually from 125 Hz to 500 Hz octave frequency bands.

  • Mid Frequency

Airflow Noise and turbulence-generated noise in a duct range from 31.5 Hz to 1000 Hz.

  • High Frequency

Damper and Diffusers Noises, they usually contribute to the overall noise in the range of 1000 Hz until 4000 Hz octave bands.

All the noise above can be avoided if we know how to design HVAC system acoustically and each of these issues must be addressed:

HVAC System Acoustically – Geonoise Instruments
  • Duct-borne Noise

The sound generated by the fan will travel along with the ductwork both upstream and downstream easily because the velocity of sound is much greater than the velocity of air in ducts.

  • Radiated Equipment Noise

Radiated equipment noise transmits through the wall or floor into the adjacent space or in the case of rooftop equipment to the environment. It is generated by vibration of the fan casing and motor.

  • Duct Break-in Noise

Noise inside ceiling plenums or from air conditioning equipment, plant room, etc, can break into the duct and then be carried into rooms or spaces downstream. So, where possible, avoid ducts passing through noisy areas as this can significantly increase noise through the air conditioning system, avoid lightweight ducts as well, replace them with heavier ducting such as sheet steel.

  • Duct Break-out Noise

Along with the ductwork, however, transmits through the wall of the duct, thus impacting the adjacent space. Generally, it happens from noise passing through the duct, aerodynamics noise from obstructions fitting in the duct, and turbulent airflow causing duct walls to vibrate and rumble radiating low-frequency airborne noise.

  • Terminal Noise

The final links in the distribution chain are the terminal air devices. These are Grilles, Diffusers, Registers, and Vent Cover that go over the duct opening in the room. Streaming air noise from diffusers and from transitions can cause additional noise in the receiving room. So that for this issue, we need to concern choosing the proper specs of supply and return air devices. We need to try to find out the NC (Noise Criteria) rating for them from their respective manufacturers.

By knowing those 5 ways of how noise occurs, it makes easier for us to categorize noise that will produce in our HVAC system design and help us in choosing what material, enclosure, duct shape and everything we need to reduce noise.

Categories
Asia Noise News Building Accoustics

Are You Stressed at Work?

Are you stressed at work?

How many times did you need to cover your ears at work? You might be stressed because you are working in a noisy environment even without realizing it.

A noisy environment is one of the primary stress triggers for the employee and it will lead to a reduction in productivity. It is dangerous for your health but it could also impact your bonus at the end of the year? Let us remind you how noisy your working environment is by mentioning some sources:

  • Copy machines
  • Obnoxious ringtone
  • Computers
  • Air Conditioning
  • Noises from outside the office buildings (Trucks, Airplanes, Highway noise, nearby constructions)
  • Laughing/Talking
  • Gossip about boss
  • Gossip about co-worker who is not invited into WhatsApp Group

Those are common noise sources that might be contributing to the noise around you. We must remember that the distinction between noise and sound is very subjective. It can be particular to each person and even depend the situation.

Noise and sound can both be dangerous for your health and can be easily measured to quantify. The graphic below shows some noise levels. Fifty decibel would be great for a working environment, exposure for long time to noise levels above 80 decibel will permanently damage your hearing.

 

How Loud is Too Loud? – Geonoise Instruments

 

After reading the graphic, please take a moment to think about how many decibels your ears have to endure daily? Let’s say that you’re working in a general business noisy office. The noise levels can be reaching up to 90 decibels because of the cumulation of various noises such as laughter, yelling, ringtones, etc. The World Health Organization (WHO) claims that exposure to noise causes stress, anxiety, depression, high blood pressure, and heart disease. Furthermore, loud sounds will damage sensitive structures of the inner ear and cause noise-induced hearing loss (NIHL).

The damage because of the noise exposure is gradual; you might not notice the signs or you ignore them until they become more apparent. Here are the symptoms of the Noise-induced Hearing Loss:

  • Sounds have become distorted or muffled
  • You can hear people, but you can’t quite understand what they’re saying
  • You can’t hear or understand speech from 3 feet away or farther
  • You must turn the volume up more than others do in order to hear it as well as they can

All checked?

Please call professional help immediately! If it is not, congratulations, you still have a good hearing. But it doesn’t guarantee you that you will be free from NIHL.

Here are the tips on how to stay sane in a noisy working environment and prevent the NIHL at the same time:

•   Bring earplugs to your work!

You only need to spend a few thousand rupiahs for this. Wearing earplugs can help you to reduce the noise by 18 – 34 decibels. It depends on the models/brand. By blocking/reducing that amount of noise, you’re still able to hear the sound around you.

•   You might want to try the Noise Cancelling Headphones

It is made for keeping the noise away from your ears. If you use this in the office, it not only will help you block the annoying noise but also will make your music sounds way better than any other headphones in the same situation. The price ranges between a hundred thousand rupiah – millions of rupiah. It is an excellent investment, though!

•   Take a break!

When the noise around you is too much to handle, give your ears a break! It gives your eara time to recover from the stressful sound and this action also a preventive way to the damage of your ears. None of them seems to be working for you? Please contact the acoustical consulting service. They will help you to find the best solutions to your problems.