Haunted house?

Last night... i went to my aunt's house at Queens near queenstown mrt... it was vacant as her family went over to their australian house to stay with their children and newborn grandchild. My maid was supposed to be cleaning the house, while my whole family go for a dip into the pool. However, my sis and i decided to stay behind to watch television at my aunt's house. So, my parents accompanied my brother down for his long awaited swim. My sis and i sat on the sofa in the living room and watched television while my maid went around the place, cleaning things wiping dust off surfaces... Suddenly, i heard a sound that resembles a "low human exhaling" sound from the direction of the living room windows, which leads to the air outside. After a while, my maid came out of the master bedroom, looking pale and extremely afraid. She said that there's a ghost in the master bedroom. I looked at her in disbelief. I told her there's no ghost around. She said there is, so I decided to go into the room to see for myself... I went there, nothing happened. Then, i came out along the corridor of the rooms, trying to give my point of view of what i think has happened. Out of a sudden, i heard the low exhaling sound from the direction of the master bedroom. Now, i began to feel uneasy and unsure how the sound came about. The maid asked me to follow her into the room to finish up the cleaning as she is scared. So i did, and nothing else happened. However, the strange thing is, my sis did not hear any sounds that we described of. When my parents came back, we told them what happened and they began to get the gitters. My father quickly lit some incense and prayed on the altar right at the spot. We unravelled all the curtains to allow sunlight to enter the rooms in the morning and in a very short while, we evacuated the place.