How to EQ Speech for Maximum Intelligibility

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Haven’t we all had stories of misheard words?  It could have been a song lyric or you misheard your spouse?  Maybe they mumbled a word or it just wasn’t clear what was said.  This has been the cause for a few hilarious moments at our dinner table.  The problem is unclear words are a distraction from the message.  In the church environment, the pastor’s words must be clear.  We can ensure this maximum intelligibility through proper speech EQ.

There are four topics to consider when it comes to the EQ’ing needs for the spoken word.  

1. Microphone location.  We are fortunate in that most pastors now use wireless microphones.  This means that the distance between the mic and their mouth is pretty consistent.  In the case of the headpiece, this is especially true.  In the case of the lapel mic, remember they should drop their chin to their chest and put the mic directly below that point.  Long ago, I was taught “a fist away from the chin.” The point here is that we want the best sound isolation we can possibly get while having a good gain structure in place.  Remember, the closer to the source, the more the proximity effect comes into the equation and you’ll need to EQ out some of that added bassiness.

2. Speaker’s natural voice.  Just as every guitar has a unique sound, so does every person.  You want to bring out the best qualities of their voice.  You don’t want them to sound like a different person.  Their vocal characteristics are also “what you have to work with.”  This means you’ll need to know how to deal with quiet speakers, bassy talkers, and nasally preachers, just to list a few.  Not everyone has a great radio voice.

3. Presence of background music.  Depending on your church, your pastor might talk with a running soundtrack.  There is definitely an art to being able to play the right music for this.  However, any type of music bed means you now have to make a space for the voice amidst the instrumentals.  Instrumentals can easily blur the spoken word so you’ll have to plan on tweaking the EQ for the musicians as well.

4. The environment.  Just because a vocal boost at 400Hz sounds good in one room doesn’t mean it will sound good in another room.  One of this site’s readers runs audio outside…in Egypt.  Any EQ work must take the environment into account.  The settings for a “quiet room” won’t be the same for an echo-y room or an outdoor venue.

Now that we’ve got those out of the way, let’s turn to…

The frequency make-up of speech

Our speaking voice has three frequency ranges that need to be understood;
1. Fundamentals.  The fundamental frequencies of speech occur roughly between 85Hz and 250Hz.
2. Vowels.  Vowels sounds contain the maximum energy and power of the voice, occurring between 350Hz and 2KHz.
3. Consonants.  Consonants occur between 1.5KHz and 4KHz.  They contain little energy but are essential to intelligibility.

In short, this means that the “power” of the voice does not equate to the intelligibility of the voice.  Think of it like this…just because a person has a booming voice doesn’t mean they are easy to understand.

Now that you understand the audio dynamics (fundamentals, etc) in a voice and the environmental concerns (background music), let’s turn to…

What you can do to provide the maximum speech intelligibility for your pastor

There are three things you can do for tackling the EQ’ing process for the spoken word.
1. Make room for the voice.  As I mentioned above, the environment makes a difference in how you EQ the spoken word.  We can only control what is coming into the mixing board, so wind and rain aside, let’s talk about music.  Mixing a large band means making space in the sonic spectrum where each instrument/vocal can sit and sound unique; and of course then blending these sounds together into a tight mix.  The spoken word needs the same treatment when music is played underneath it.  This can happen in two ways;
A. Adjust volume.  This can be done using compression or simple volume adjustments.  The general rule-of-thumb is the music is there to support the spoken word – to sit underneath it.  Therefore, look to cut volume levels of instruments before you boost the volume of the speaker.  You can also use compression to bring volume levels up and down as you wish.
B. Adjust the mix.  Cut the frequencies of the instruments where they are the same as that of the speaker.  Boost the spoken word EQ in those areas a little if needed to present the music and the voice as two distinct sounds.

2. Know sibilance and how to avoid it.  Sssssssibilance in vocals is when the sound of the letter “S” sounds more like a hissing snake.  You can accentuate vowel sounds / add presence by increasing the EQ in the 4.5Khz to 6Khz.  However, the “S” sound lives between 5Kkz and 7Khz.  Therefore, be careful when adding presence because you can easily go from a great sound to a hissy sound.

3. Focus on vocal quality.  There is no simple 1-2-3 process to EQ’ing the spoken word.  Therefore, take these points into consideration;

  • Roll off the low frequencies if the proximity effect is causing unusual bassiness.
  • Don’t roll off so much low end as the voice loses some of its umph.  Yes, I’m using “umph” as a technical word.
  • Boost in the 1KHz to 5KHz range for improving intelligibility and clarity.
  • Boost in the 3Khz to 6Khz range to add brightness.  This can help with speakers with poor intonation.
  • Boost in the 4.5Khz to 6Khz range to add presence.  Note that too much boosting in this area can produce a thin lifeless sound.
  • Boost in the 100Hz to 250Hz for a boomy effect.

 In case your head is about to explode from an information overload, remember these key points;

  • The above points can contradict each other.  There is no hard and fast rule.  Mixing is as much an art as a science.  Trust your ears over everything else.
  • It’s possible that once you EQ the vocal channel that it’s a little lacking in the low end.  Boost it a bit give it that full sound.  Again, trust your ears.  Close your eyes and ask yourself if it a) sounds natural and b) sounds clear.

Finally

EQ’ing the spoken word is about improving the quality of the sound so it sounds clear, is easy to understand, and sounds natural.

So much of our mix time goes towards the band.  Make sure you spend those few crucial minutes working on the pastor’s vocal as well.  Church was about the sermon long before music, skits, and cool videos rolled onto the scene.

Check out the Vocal Microphone and Vocal EQ Resource Page!

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Comments

  1. ChrisJohn says

    Thanks Chris for your great article. I mainly mix for singers in (amateur) musical theatre situations, and sometimes I find with females that a slight boost around 350 to 450 Hz will make a thin voice more fuller sounding. I recently eq ed the cast of a play with songs while they were singing, with a desk that only had semi parametric eq ing for the mids. However what sounded good eq wise when they were singing I gradually realised, in rehearsal, was giving a slightly muddy sound with the dialogue, and also not helped because of the fake Irish accents the cast were using, made them at times not easy to understand. Some of this was down to diction not being as good as it could be, but some of the issue was with the eq ing. To remedy this, in most cases, but especially with the guys, I took a few dB off around the 400 Hz area, and it made a huge improvement with the clarity. It was a trade off, however there was a lot of dialogue that needed to be to be understood by the audience, and the singing of songs still sounded okay with the new eq ing. So I find I am always listening and learning with sound!

    • says

      ChrisJohn, you bring up a point that many don’t realize; the spoken word and the singing voice are uniquely different and must be treated as such. You’ve got a hard job…thank you for devoting your energy so the audience has the best experience!

  2. Mark R says

    Hi Chris, thanks for the article. I have a question: you state that vowels are between 350Hz and 2KHz. Then later in the article you state “You can accentuate vowel sounds / add presence by increasing the EQ in the 4.5Khz to 6Khz”. I’m confused. Wouldn’t you have to boost in the 350-2K range to accentuate vowels? Or are you boosting the vowel harmonics or something?

  3. Mike P says

    This is an excellent post. Thank you Chris.

    I will be re visiting my eq for the spoken word again this week.

  4. Chris says

    I didn't mention something equally important as boosting and that's cutting.  Many will say cut first then boost.  I started a section on that but thought the article was getting too long. 

    Thanks for your kind words.

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