SINGAPORE - When he heard about a resident's complaint over the sound of chairs being dragged from a flat above, Marine Parade GRC MP Tan Chuan-Jin thought it was a neighbourly dispute.

However, he found out that there was no one living in the flat in question, as the former occupant had died and the apartment was empty.

Mr Tan, who is also Speaker of Parliament, wrote in a Facebook post on Tuesday night (Dec 12) that he encounters issues that may be beyond an MP's ability from time to time.

"And I mean way beyond," he quipped.

Mr Tan, 48, told The Straits Times on Wednesday that as an MP, he receives feedback from time to time that seems to "defy conventional explanation".

Some sounds that are commonly heard in Housing Board flats include the sound of marbles dropping or rolling, furniture shifting and footsteps.

"There are the usual explanations such as expansion and contraction of pipes and sounds transmitted from other units," he said. "Even cats mewing can sound like babies crying."

Mr Tan said that in most cases, the noises are caused by residents or are misperceived.

"Sometimes, neighbours can be less than considerate, while in some cases, there may be some mental health issues involved either on the part of the person causing the noise or the one perceiving it," he said.

However, he said he personally encountered a few cases where the sounds were odd and there did not seem to be a scientific reason behind it.

"For example, there is a block where there is a loud banging sound in the wee hours of the morning, but no one seems to be able to narrow it down to a specific source," he said. "Despite repeated efforts, this continues to remain a mystery to us all."

However, Mr Tan stressed that residents in a community "just need to learn to live and let live, be as considerate as we can, and reach out to know our neighbours better".

"It really does make a difference when we do have a positive relationship with those living around us," he said.

In 2005, The Straits Times published an article that sought to address the mystery of falling marbles heard in HDB flats.

Structural engineers pointed to two probable causes: The plumbing and the concrete walls and floors.

Concrete floors may contract at night, giving off creaking sounds. Furthermore, sound travels and is distorted as it passes through concrete walls and floors.

One engineer said the sounds came from the plumbing in what is called water hammer.

Water hammer occurs when water flow is shut off suddenly like when the toilet is flushed. This change in pressure rattles the piping and creates "clanging" sounds, which may sound like marbles dropping after distortion through concrete walls.

The report was published as a follow-up to a letter from a reader who said he endured the sound of marbles being dropped on the floor of the unit above for 15 years.

After the letter was published, people started discussing - both offline and online - the possible reasons for the marble dropping sounds.

One popular theory was that HDB had placed marbles between floors so that playful spirits would be so distracted playing with them, residents will be left in peace.

HDB said in a letter to ST then: "To date, we have not received any feedback on the sound of dropping marbles where there has not been any attributable cause."

A check on HDB's website reveals only guidelines on noise levels.

Residents are advised to "be considerate towards neighbours and observe the quiet hours between 10.30pm and 7am".

Some of the guidelines it offers include not dragging furniture across the floor, ensuring that children do not make too much noise while playing and using rubber stoppers on the base of furniture to absorb noise.