The sound colour spectrum - white, pink and brown - have all been shown to help improve sleep. Choosing which one will help you sleep best can be hard to decide, so briefly I'll describe the difference.
<ol>
 	<li><strong>White noise</strong> - White noise contains a range of frequencies, all evenly distributed. Having the frequencies evenly distributed makes white noise the perfect sound cancelling noise. White noise is the most common noise cancelling sound, and has also been recognised for its sound cancelling properties for the longest time. However, the high frequencies can be perceived as harsh, which can be counter productive if you want to use it to help you sleep.</li>
 	<li><strong>Pink noise</strong> - Pink noise contains the same range of frequencies to white noise, however, it has greater emphasis on low bassy sounds. The high frequencies are still present in pink noise, but they are less pronounced. Pink noise is a softer sound to white noise.</li>
 	<li><strong>Brown noise</strong> - Brown noise has a greater emphasis on the low frequency sounds, and contains no high frequency sounds. The reduces range of frequency makes brown noise slightly less effective as a noise cancellation sound. However, if the sound you are trying to mask has a low frequency (such as boots on upstairs floorboards) it is still effective. Brown noise is generally more associated with relaxing, but has been shown to be an effective sleep aid.</li>
 	<li></li>
</ol>
<h2>Which is the best for sleep?</h2>
The unhelpful answer is, "<em>it depends</em>". It depends on what noises you are trying to block out and what noises you find irritating. However, broadly speaking, <strong>pink noise</strong> will be the best to help you sleep. White noise is the most effective noise blocking sound. Research supports its claims as a sleep aid, and it can mask a range of frequencies. However, the high frequencies may be too harsh for you, which can make getting to sleep in the first place very difficult. Brown noise, although thought to be the more relaxing of the sounds, lacks the high frequency ranges and so it cannot mask some sounds as effectively as white or pink noise. Pink noise on the other hand, is a safe middle ground.

However, you know your specific situation much better than me. Have a think about the sound you are trying to block, and how loud it is. White noise may be the only answer, but brown noise may be all you need...The only way to truly know is to try each sound.

Fortunately, most sound machines are capable of producing white, pink and brown noises. The most successful (thanks to its non-looping and randomised technology) is the <a href="https://www.soundofsleep.co.uk/product/lectrofan/">LectroFan</a>. The lectroFan produces a range of white, pink and brown noises along with several fan sounds.

Other machines include the Sound+Sleep SE, which produces all the sounds the LectroFan produces, but also contains a range of adaptive natural sounds. These include a cracking fire, the ocean and medow. These sounds are extremely relaxing and aswell as helping to mask sounds, help to distract you from the stressful thoughts that can prevent you drifting off to sleep.