A monotone voice is one which doesn’t vary much in pitch; the range of intonation is much flatter.
Andy Murray is an extreme example of this – he’s the most monotone man in our database. However, a lot of actors have this kind of voice too – Tom Hiddleston, Harrison Ford and Alan Rickman are all good examples.

Well, sorry to get to the sales pitch so early on, but there’s only really one way of telling, objectively, if you have a monotone voice. Vocular scans your voice recording to tell you how varied or monotone your voice is, as well as other stuff like your voice depth and how much vocal fry you speak with. You can see an example of the analysis below. Anything under 10Hz we classify as monotone and anything above 20Hz is fairly varied. 30Hz tends to be so varied you only see it in a few speakers like David Attenborough.

Testosterone definitely seems to be one cause. Men tend to have more monotone voices than women, and this change kicks in during puberty – as the voice drops in pitch, it becomes flatter and less intonated too. Similarly, a study which pitted men against each other found that those with higher testosterone levels had more monotone voices, and these same men also had stronger arms and sounded more dominant than the other men.

This is something we see in Vocular’s database too. Not only did the 50 most monotone voices all belong to men, the Top 3 all belonged from former #1 tennis players: namely Andy Murray, Novak Djokovic and Roger Federer. So it fits the brief of a competitive personality almost too well…

As for other causes, it’s hard to say for sure but a flatter tone has been correlated with a couple of surprising things. The first is that men with monotone voices seemed to be healthier than other men. A study on immunity found that these men gave themselves better general health ratings, had higher future health expectations, and greater levels of a salivary antibody, sIgA, which has been linked lower rates of cancer and respiratory disease.

Another surprising connection was that men with monotone voices tended to have more sexual partners, even though these voices were rated as no more attractive than the more varying voices. More on this in the next question…

This one really depends who you are and where you are. If you’re a man in the English-speaking world, then being monotone doesn’t seem to make a difference to your vocal attractiveness. Studies don’t tend to find a correlation and you see this in the voices people claim to like – for every Alan Rickman or Tom Hiddleston there’s a Morgan Freeman or David Attenborough.

However, studies done in French, Chinese or Japanese all find a monotone voice to be unattractive in both sexes. This is probably a cultural thing stemming from the language – for example, Mandarin is a tonal language and relies on changes in pitch to give words their literal meaning, so a monotone voice sounds quite alien in China.

This also fits the general observation that familiar-sounding voices tend to sound more attractive. Even though everyone thinks they hate the sound of their own voice, they most likely don’t. If you take a recording of someone, mix it in with a bunch of voices all saying the same thing, then get that person to rate how attractive they find each voice, they generally give their own voice a high rating.

For women in the English-speaking world, annoyingly I could only find one study, but this found that, like with men, being monotone didn’t make a meaningful difference. You can see this in the table below (where F0-variance refers to how much intonation a voice has). In fact, none of the objective measures these researchers examined had a meaningful effect on how attractive women sounded. You can see this below, where asterisks indicate significant results.

From Zuckerman & Miyake (1993: 17)

Well, there are basically two modes of sexual selection. Everybody knows the first, which is selection by the opposite sex (i.e. a particular trait evolves because the opposite sex finds it attractive). However, there is a kind of selection from the same sex too. Some traits emerge because they scare off love rivals. Beards are a classic example of this – they tend to make men look less attractive on average, however they also make men look more threatening, which makes it easier to stop other men from getting in your way. Basically, sexual selection is magnetic: it’s not just about attraction, it’s also about repulsion.

If a monotone voice really signifies health and doesn’t usually make voices less attractive, then why is it something people complain about, like nasality or vocal fry? Well, I think there’s a bit of a linguistic trick going on here. See, a monotone voice is not the same thing as a monotonous voice, there’s actually almost no correlation between these two things. You can see this in table below, where the r-value is -.02. That’s about as uncorrelated as it gets.

From Zuckerman & Miyake (1993: 15)

1. Strengthen your Neck Muscles

I’ve seen a lot of talk about this online, so I wanted to start by confirming here: this truly does work. Actually, it’s my favourite method of all of them.

If you put your hand on your throat, you’ll feel two long muscles which run down from behind your ear to your collarbone. These are your sternocleidomastoids, and when they get tense they tug on your vocal chords, resulting in a higher note. Relax these and, logically enough, your voice gets lower.

One recommended way of doing this is by making the neck muscles stronger. Stronger muscles are better at meeting their daily demands and therefore less likely to tighten up throughout the day. I was interested in this idea, so I thought I’d test it out.

Every day, at 2 o’clock and in the same room, I recorded a sample of my voice and wrote down the figures. I chose 2pm because I wanted the ‘morning effect’ of my voice to have worn off and I knew I wouldn’t have been drinking alcohol around that time. After the recording, every other day, I’d do 3 sets of 20 reps of crunches, where I lay on my bench and slowly nodded my head from horizontal to vertical, tucking in my chin – like doing sit-ups with your neck.

And it worked. Here’s a chart I made with Vocular.

As you can see, by all four metrics, my voice did deepen over time. My matches completely changed too.

More compellingly, my voice actually got higher before it got lower. It starts at about 105Hz, then shoots up to 113Hz and stays high for a week, before it gradually deepened month after month to the current pitch of 89Hz. That’s like going from Edward Norton, to Justin Bieber, to Jon Hamm.

This fits the idea that strong neck muscles give you a deeper voice. The exercises first made my neck weaker, like any muscle when you start training it. So my voice got higher. Then, as I continued with the exercises, it got used to the strain and became stronger, and my pitch dropped.

I should add that I also stretch my neck to relieve any tension that might build up with the exercises. So if you’re thinking of doing this, that’s something to keep an eye on. In fact, this guy on Reddit seems to have a routine which worked really well for him and seems to focus more on stretching.

2. Breathe from the Diaphragm

Ever noticed how your shoulders bob up and down as you breathe in and out?

If you’re have, you’re doing it wrong. This is a thing called ‘shallow breathing’ and it’s something most people are guilty of. While it seems as good as any method, this kind of breath shifts effort to the upper half of the torso, putting tension on the neck and vocal chords.

Instead, breathe with the muscle that’s designed to do it: the diaphragm. As you inhale, try to shift the effort downward so your stomach flexes out while your shoulders remain completely still. Feel as though the air is being summoned by your abs.

I know it’s quite hard to follow in writing, so Eric Arceneaux does a very good job of explaining this.

This one correction had the greatest impact on my voice depth – but, like any bad habit, it requires a conscious effort to overcome it. You may want to try something to remind yourself when you’re creeping back to your old ways. One vocal coach has created the Singing-Belt to do this, although it’s expensive so using kinesiology tape or a tight T-shirt might work better.

3. Aspirate

You can try this one for yourself and immediately see its effect. Open Vocular and enable the Pitch Tracker in Settings, then speak to the microphone in your normal voice and see what numbers come up.

Now try talking in a breathier, more aspirated kind of way, as if you’re speaking through a sigh. If you need someone to copy, Tom Hiddleston’s a pretty good example.

4. Drink More Water

Please don’t skip over this section, because it’s a lot more important than you might think. You know how the depth of your voice is partly caused by the size of your vocal chords? Well, dehydration literally shrinks your vocal chords. The loss of water equates to a loss of mass, leaving you with thinner, squeakier vocal chords.

And, strikingly, most people are dehydrated. A recent study found that 75% of Americans fell far below the recommended daily intake, which, again, gives us a majority of people speaking with higher voices than they ought to be.

The solution is to make things easier for yourself. If you work at a desk, get a jug (one that can hold 3-4 litres) and fill it every morning. Not only will this encourage you to drink more because it’s there, it’ll bring the water to room temperature which stops the throat contracting from the cold.

5. Be More Monotone

I’ve noticed a few names that come up time and time again when discussing voice depth. One of these names is Clint Eastwood. But the weird thing here is that, in terms of pitch, Eastwood doesn’t have a deep voice. It’s about average.

However, one thing Eastwood has in spades in monotony. This is a very manly trait – in fact, a recent study found that men with monotone voices tend to have more sexual partners than those who don’t. So it may be that the masculinity of a monotone voice tricks people into thinking that voice is deep as well.

1. Women are more attracted to men with deep voices – and this attraction is strongest among prettier, more feminine women. In fact, women prefer a masculine voice more strongly and more unanimously to a masculine face. This might lead you to think you should be the next Barry White, but a recent study found that the most attractive male voices were the ones around 96Hz (that’s deeper than average, but not incredibly so.) Once this average pitch fell into the 80s, women preferred a higher voice.

Barack Obama, Alec Baldwin, Jason Momoa, Patrick Stewart, Morgan Freeman and Gerard Butler all speak with a median pitch of ~96 Hz

2. Deep-voiced men are rated as being significantly more dominant, both physically and socially, to men with higher voices – and men who believe themselves to be more dominant subconsciously lower their tone when faced with competition.

This is probably why powerful characters such as Darth Vader or Smaug are traditionally given very deep voices. They’re supposed to intimidate on a very primal level, and a low pitch and low variance is the best recipe for that.

4. People prefer voting for politicians with deep voices, especially during wartime. Most famously, British prime minister Margaret Thatcher underwent vocal coaching to lower her voice by a whopping 46Hz, more than half the difference between male and female voices.

7. Lowering the pitch of your voice makes you feel more powerful. Much in the same way that certain ‘power poses’ boost confidence and reduce anxiety, researchers found that “participants who lowered their voice pitch perceived themselves as possessing more powerful traits”. They also found that they gained, in their own words, “a higher level of abstract thinking”, which is associated with people in high power positions.