Like musical trends at home, the daily sounds of Baghdad are always changing.

Two years ago, we used to hear a lot of mortars. For some reason, I haven't heard any so far on this trip. Maybe the insurgents ran out, or perhaps it's not worth the risk of using them since the U.S. military can quickly pinpoint a mortar launch site.

By last summer, the sounds of the city had changed again. Early morning car bombs were our wakeup call.

But on my arrival last Friday — my first visit to Iraq in nearly six months — I heard the sound of silence.

There's a regular Friday curfew that keeps vehicles off the streets but allows people to walk to the mosque. It was put in place after insurgents realized they could use car bombs to kill worshippers as they waited to get inside the mosques. Late Friday night, the Iraqi government announced that the curfew was being extended for 36 hours — for both civilians and vehicles. So the weekend was unnaturally quiet.

But in Baghdad, "quiet" isn't necessarily a good thing. Sectarian death squads are increasingly becoming Iraq's silent killers. City residents don't think this silence is the calm before the storm; they think the silence is the storm, and it's killing hundreds, sometimes thousands of people each month.

The death squads are mostly Shiite, although some are Sunni. The Shiite groups often set up fake army or police checkpoints and round up dozens of people at a time. Anyone captured who's a Shiite will be released. The captured Sunni might be taken before a strict Islamic court and sentenced to death with the blessing of a Muslim cleric. Of course, not everyone who gets kidnapped ends up dead. But those who do have a life expectancy of between four hours and two days from abduction to death, according to a senior coalition intelligence official. During those hours or days they're often brutally tortured. For many, death must be a relief.

We're in the middle of Ramadan, the Muslim holy month, when people fast all day — but then traditionally gather for family meals (called an "iftar") after sunset. Some of our Iraqi staff are Christians, but most are Muslim, so they're fasting all day — not even drinking water, although the temperature is still over 100 degrees.

The current situation has made Ramadan a bleak time for most families here in Baghdad. Iftars used to be highly anticipated celebrations, when friends and family would come over to break the fast. Dinner would last late into the night. This year is worse than ever. Electricity outages mean there's no way to prepare the iftar meal — and candles aren't a very effective form of cooking. Guests are too afraid to leave their homes, fearing they might become just another statistic in Baghdad's daily death toll.

Ramadan is also a tough time for U.S. forces in Baghdad. Military officials predicted a rise in violence, and they were right on the money. According to one U.S. commander, the first week of Ramadan was the worst for suicide bombings since the invasion of Iraq back in 2003. Over the past few days more than a dozen U.S. personnel have been killed. Even during this most deeply religious time of year for Muslims, there's no letup in violence.

David Mac Dougall is a freelance reporter for FOX News in Baghdad.