Noises can be distracting when you're trying to get work done, and using white noise can help mask background office sounds.  Sure you could get a white noise machine or turn on a fan, but there are some nice free white noise generators available online.

One that powered me through a recent spate of noisy library building repair was the free online Sound Mixer tool from the American Tinnitus Association.  You can choose a sound from 1 or all 4 columns, and use the sliders to adjust the amount of each sound you want in the mix,

P.S. I do NOT recommend the lemur!

Other white noise generators I've used that you might like:

• iSerenity
  • white noise and ambient sound (including thunder, rain, purring, birds, ocean, waterfall, typewriter, fire, restaurant, hairdryer, vacuum, wind chime, and fan)
• SimplyNoise (I also have the app on my phone)
  • "White Noise - Contains sound across all frequencies. White noise is the most effective at blocking distractions because it covers the largest spectrum range. It's great for reading, writing, studying, and anything else that requires focus."
  • "Pink Noise - A blend of high and low frequencies that produce a mesmerizing waterfall effect. Pink noise is great for melting away stress while keeping you alert and energized. The airy pulse creates a therapeutic environment that relaxes your mind and body."
  • "Brown Noise - Utilizes the lower sound frequencies to generate a deep ambient rumble. Brown noise is excellent for aiding sleep, pacifying children and pets, and even masking Tinnitus. It's also great for breaking in audio equipment and soothing migraines."

Hat tip to my Ear, Nose and Throat doctor for recommending the American Tinnitus Association website's resources. Here's my current sound mix: