Distorted sound using airplay

Ok, if I understand you correctly, your Samsung TV is AirPlay-enabled and you can stream to it directly without either requiring an Apple TV or a cable.

One thing to keep in mind when streaming with AirPlay over a wireless connection, is that the stream will first go from your MBA to your wireless router, and then, go from the router to the TV. That means if your router is in another room from your TV & MBA, that that stream must pass through the wall, separating those rooms, multiple times. If that wall is constructed of material that does not allow the Wi-Fi signal to traverse it easily, it will affect the overall signal quality of that stream, and thus, the stream's quality as well. This may be why you are hearing distorted sound when using your MBA in this location.

One test is to bring the MBA into the same room as the wireless router. Leave the MBA at this location and start a stream. Go back to the room with the TV and listen to the playback. Did the distorted sound stop or get reduced significantly?

No need to borrow a cable at this point. I just want to understand how you are connecting your devices to your Samsung TV. If I understand you correctly, you are NOT using an Apple TV, but are connecting both of these devices via a wireless connection to the TV. Is that correct?

Since you're currently not having any issues with your iPhone, let's concentrate on your MacBook Air (MBA). Where do normally use your MBA when you try streaming to the TV? Same room, different room, or different floor? Regardless, what is the make & model of your wireless router that is providing your wireless network? Where is it located, in relation to the MBA, when streaming?

Ok, thanks for clarifying that. I asked because AirPlay will work differently for these two devices. The other question I meant to ask is are you using an Apple TV to receive the AirPlay stream or either/both of these devices connected directly by HDMI/adapter to the HDTV?

When watching movies from your MacBook Air, where are the movies located? That is are they located on the notebook itself, on an external drive, or from a source on the Internet?