Environment
It’s obvious that you’ll need somewhere quiet, but it’s equally important to reduce reverberation (reflection of sound from surrounding surfaces).
Bad:
- Hard floors such as wood or tiles
- Bare walls
- A desk or table with a large horizontal surface
Good:
- Carpet or rugs
- Soft furnishings such as a bed, sofa, heavy curtains
Best:
- Create a mini-studio by arranging sound-absorbing objects behind and around the microphone.
- A simple option is to open your wardrobe doors. Place the microphone inside the wardrobe (not touching any clothes) and record facing into it.
- Another option is to arrange cushions in a box shape and place the microphone inside.
- You are trying to make something that works like this or this without spending any money.
Microphone
You generally don’t want to use the microphone built in to your laptop. The laptop is a source of noise, and you’ll also find it hard to get it into a convenient close-talking position.
A surprisingly good option is the microphone built in to wired Apple iPhone earbuds (the type with a 3.5mm 4-ring jack connector), which will plug in to a Mac’s headphone socket. You’ll need a way of mounting it in a suitable position (do not hold it in your hand, or use it hanging from your ear – it will move about). You could use an elastic band to attach it to a suitable object such as a tall bottle. Other brands of similar microphone might also be good, although we haven’t tested any.
If you don’t have one of those Apple microphones, you need some other external microphone. Unless you really know what you are doing (in which case you probably don’t need this guide), this will be a microphone that connects directly to a USB port.
If you’re in the market for a new microphone for podcasting or videoconferencing, then the Blue Snowball iCE is excellent at that price point. Amazon’s Basics Desktop Mini Condenser Microphone is also very good value.
Be aware that some USB headsets produced specifically for video conferencing have a rather narrow bandwidth – make a test recording and inspect the spectrogram to find out.
Pop shield
Unless you have really excellent microphone technique, you are likely to get “popping” with plosive sounds, as a puff of air hits the microphone. The solution to this is a pop shield (also called a pop filter) but you can make your own then set it up like this.
If you don’t want to use a pop shield, then good microphone placement and voice talent technique is essential. One option is to suspend the microphone from above at eye level and speak so that your breath passes below it, but this will get in the way of reading a script. Another option is at or just below mouth level and slightly to one side. Experiment and make test recordings.
Laptop
You will probably be recording on to your laptop from an external microphone, and you’ll also be reading the prompts from the laptop screen. Try to place the laptop in a way that minimises noise picked up by the microphone. Use something sound absorbent to block the noise if necessary. As always, making test recordings with a variety of setups will help you decide what’s best.
Automatic Gain Control (AGC)
Some operating systems and/or audio hardware may have a feature which aims to continuously adjust recording volume levels automatically in response to how loud the sound reaching the microphone is. This is called Automatic Gain Control, and it may be switched on by default on your machine. This can work well for things like Zoom calls (though it can also cause problems when it doesn’t work properly!), but for recording speech data to build a speech synthesis voice it is bad for two reasons:
- continuously changing the recording gain could potentially introduce inconsistency into the recordings – for example, a short sequence of naturally loud phones may cause the following phones to be recorded quieter than they should be
- recording noise can be made louder at quiet points (the noise floor can be raised)
Therefore, it is important to make sure you don’t have AGC active when recording your own speech data. It does not seem this is a problem on Macs, but you’ll find online instructions for how to disable this on Windows and Linux (e.g. pulseaudio), for example:
