I bought a USB microphone off Amazon (~$130), and plugged it into my high-end Mac (OS 10.14, Mojave). The sound quality is great, but it is very quiet - with the input volume slider in System Preferences all the way to the right, my other mics (like the ones in cheap webcams) have sound bars that go all the way to the right when I talk 3 feet away, while this one, right near my face, is only showing the first few bars of the volume scale. The company has replaced it, thinking it may be a bad unit - same exact outcome. Is it really the hardware, or is there some setting somewhere I am not finding? How can this thing be so much quieter than the cheap webcam mics?
What is the make and model number of the mic?
Which model is your Mac?
How is the mic connected to the Mac?
It’s a Maono “USB Microphone with Studio Headphone Set 192kHz/24 bit MAONO AU-A04H Vocal Condenser Cardioid Podcast Mic Compatible with Mac and Windows, YouTube, Gaming, Livestreaming, Voice Over” (https://amzn.to/3aL6Gy4). It was connected by a USB cable to a powered USB3 hub, and I just tried plugging it directly to a USB hub and I think it gained one bar of volume just from that. The Mac is an iMac Pro (2017), 3.5 GHz 6-Core Intel Xeon E5, 64 GB 2800 MHz DDR4.
That looks like a “side address” microphone, which means that you need to speak into the “front” of the mic, not into the end of the mic.
yeah… I’ve tried it every which orientation - just still super low signal overall 
USB microphones frequently have a fairly low signal level because they have to be able to handle loud people without distorting.
Perhaps you could post a short test recording so we can see what sort of signal level you are getting:
Position the mic about 15 cm in front of your face, with the front of the mic facing your mouth.
Hit record and count in a clear voice: “1, 2, 3, 4, 5” then Stop.
Export as a WAV file and attach the WAV file to your reply (see: https://forum.audacityteam.org/t/how-to-post-an-audio-sample/29851/1)
Here it is. It’s better than it was before (I found a very specific angle) but it’s still pretty quiet and hits only about a third of the max bars on the system preferences sound meter. Here’s the file - is that all that can be expected (at least, background noise is low!) or is there a way to make it louder?
because they have to be able to handle loud people without distorting.
And not just “people” but loud-amplified guitars, etc. 
But the good news is - Digital recording levels are not that critical as long as you avoid clipping. (The ADCs & DACs clip at exactly 0dB.) You’re usually going to leave some headroom and amplify digitally anyway. It is important to have strong acoustic and analog signals for a good signal-to-noise ratio.
If the mic is too sensitive you’ll overload (clip) the analog-to-digital converter inside the microphone and reducing the digital level in software won’t remove the distortion.
Some USB “podcast mics” have an analog recording level control. Good USB audio interfaces (designed for use with good analog stage/studio mics) also have a recording level knob.
A bit of context. I’m using this for interviews and meetings via Zoom and such, so it’s all happening live and being recorded (by someone on the other end of the teleconference), so I don’t have the opportunity to amplify after the fact. I need it to work well live (as my cheap microphones do, but the sound quality isn’t very good there).
Just to confirm you are announcing into the side grill that has the company name. It is a side-fire, directional microphone.
To read this back to you:
The purchase comes with articulated desk stand, USB cable, vibration and shock mount, pop and blast filter, wind sock, and large production headphones, all for $99.
The microphone was free.
Koz
Is it still quiet in Apple (upper left) > System Preferences > Sound > Input?
Audacity gets its sound from the Mac, not the microphone.
Koz
There’s another caution, too. Zoom and other communications programs like to take over the machine’s sound services. Did you get an actual complaint from one of the clients?
Koz
The seller does have the cheek to list the “MAGNET RING” as a feature, (which retails at <50¢ ).
(If that feature gets listed then I think they would have said it had a pad switch if it had one,
They don’t, but worth a look to see if it does).
yes, here’s what I see when I’m talking normally:
the other mics go all the way to the right of the bars.
yes, people say it’s quiet, and I’m trying it in Audacity or Quicktime audio recordings and it is indeed quite soft.
I don’t see it on the outside of the mic anywhere; any chance it’s internal somewhere and I should take it apart?
No ! 
: It will be on the outside, if it had one.
See … https ://www. google.com/search?hl=en&tbm=isch&q=pad+switch+microphone
( if it had one, and it was switched on, that would make the mic 10/20dB quieter)
If it had a pad switch, it would be on the outside.
I think the problem is that it is a quiet mic. Either you need a more sensitive mic for your voice, or a louder voice for the mic. Considering the amount of stuff that’s included, it was not a bad price, but the mic is one place that you really shouldn’t be cutting too many corners.
You seem to have a fairly quiet voice, so if you go with a USB mic, you really need one that has a gain control to give the signal a bit of boost.
I would also highly recommend using a mic that has a headphone socket (so that your headphones plug into the microphone). This is essential if you want to do overdub recording (recording more than one track).
is there a recommendation? I don’t do music, multiple tracks, or anything fancy - just talking. I thought $130 would be reasonable but maybe not? What is a good mic for this purpose?
When there are “unnatural” Amazon- reviews it’s a bad sign …
https://reviewmeta.com/amazon/B07VYJ4TV2
https://www.fakespot.com/product/usb-microphone-with-studio-headphone-set-192khz-24-bit-maono-a04h-vocal-condenser-cardioid-podcast-mic-for-mac-and-windows-youtube-gaming-livestreaming-voice-over