How Sound Spreads Is Reflected In Large Open Spaces

In a room, we typically hear that a voice is louder than in an open area. This is the effect of reflected sounds which comes out of the mouth and is reflected on the walls and finally comes back into the receiver’s ear. Those sound reflections enhance the voice of people so that louder sound and greater clarity is gained indoors.

The sound received indoors can be divided into two parts. If the sound arrives at the receiver directly, it is called a “direct sound”. If the sound is reflected on a surface and finally received by the listener, it is called “reflected sound.”


The further you stand from the sound source, the less you will hear it. Because the voice spreads like a constantly blowing balloon. The bigger the balloon is blown, the thinner it will be. The transmission of the reflected sound also follows this principle. Therefore, the later the reflected sound reaches the listener’s ears, the softer the final sound will be heard.

With the development of construction technology, some extra-large spaces have been built to accommodate more and more complex functions. It can be imaged that if the distance between the talker and the listener is the same, the larger room you stay in, the smaller voice the listener hears. When a space is large to a certain extent, is the reflected sound still important or the sound in extra-large spaces just spread as in the open area?

On-site measurements were carried out in four cases, such as the measurement. The volume of the four cases varies from 7000 to 190,000 m3, representing ordinary to extra-large spaces. Computer simulations were also conducted using image method to obtain more details.

The results show that the first reflection from the floor (FRFF) is significantly larger than other reflections because both the source and receiver are usually closer to the floor which can be used to enhance the existing prediction model.


The received sound energy in a room can be divided into three parts, which are direct sound, first reflection from the floor and other reflected sounds. They all occupy a significant proportion of sound energy that cannot be ignored in the prediction. The direct sound attenuates exponentially along the source-receiver distance, which is due to the spherical spreading of point sound source. The reflected energy, which is also called the “reverberant energy”, also attenuates near-exponentially, especially when there is a lot of sound absorbing material in the space. As to the FRFF, it is lower than the direct sound in the near-source area and almost the same in the far-source area. This suggests that some furniture or carpeting may be useful for reducing the noise in extra-large spaces.

A modified prediction model of sound pressure level has been developed based on the FRFF and obtains a good prediction accuracy. This prediction model can be used to predict the sound pressure level in extra-large spaces and it is also important for acoustic design and crowd noise control.

These findings are described in the article entitled Characteristics and prediction of sound level in extra-large spaces, recently published in the journal Applied Acoustics. This work was led by Jian Kang from University of Sheffield, UK, in collaboration with Chao Wang (Tianjin University, China), Hui Ma (Tianjin University, China) and Yue Wu (Harbin Institute of Technology, China).



Discontinuing Contact Precautions For Multi-Drug Resistant Microorganisms In The Inpatient Setting

Imagine that you are admitted to a hospital and acquire a healthcare-associated infection (HAI) due to the same bacteria that […]

Are Ecological Interactions More Intense In The Tropics?

THE QUESTION When we think about a tropical site, what commonly comes in mind is heat, rainforests, beaches, and colorful […]

How Particles Contribute To Cloud Formation

Clouds are one of the main factors influencing the atmospheric system: they are one of the most important elements in […]

Using Remote Sensing To Measure Crop Growth And Management

In most East and Southeast Asia countries, mosaic crop production systems usually consist of relatively small land holdings ( < […]

Pinocembrin: A Natural Compound For Treatment Of Acute Intracerebral Hemorrhage And Traumatic Brain Injury

In the past decades, hospital admissions for acute brain injury have continued to rise. For instance, intracerebral hemorrhage (ICH) and […]

An Important Community In Restoration Efforts To Protect The American Chestnut Tree

The American chestnut once dominated the eastern forests of the United States. A fungal pathogen, Cryphonectria parasitica, was introduced to […]

Avalanche Destruction Zone & Its Impact On Old Growth Forests

Mountains are exposed to mass movements such as landslides, debris flows, and snow avalanches. These hazards affect valley slopes and […]

Science Trends is a popular source of science news and education around the world. We cover everything from solar power cell technology to climate change to cancer research. We help hundreds of thousands of people every month learn about the world we live in and the latest scientific breakthroughs. Want to know more?