Any alternative to Radio Shack sound level meter?

I got UMIK-1  (USB microphone)
https://www.minidsp.com/products/acoustic-measurement/umik-1

Then I downloaded Room EQ Wizard (free program):
https://www.roomeqwizard.com/

When you enter microphone serial # it downloads calibration data.  It contains two text files - dB corrections at different frequencies for directional (microphone pointing forward) and omnidirectional (microphone pointing up) modes.  

It allows to automatically sweep frequencies and record chart, but it works only if you can connect computer to your system (I use computer for playback anyway). 

@oldears  I did few frequency sweeps only, so far (results  look pretty bad), but program has a lot of tools:

 It includes tools for generating audio test signals; measuring SPL and impedance; measuring frequency and impulse responses; measuring distortion; generating phase, group delay and spectral decay plots, waterfalls, spectrograms and energy-time curves; generating real time analyser (RTA) plots; calculating reverberation times; calculating Thiele-Small parameters; determining the frequencies and decay times of modal resonances; displaying equaliser responses and automatically adjusting the settings of parametric equalisers to counter the effects of room modes and adjust responses to match a target curve.

mijostyn, thank you.  I know there is something wrong with my room response, but I will fix it later.  At least I have tool. My room is too reflective.  I don't hear any particular resonances but listening louder makes sound less clean.  It is most likely multiple echo, that it is reduced at low volume levels (further echoes fall below hearing threshold).