[BUG] no sound in MP3 file

[kiricheglov]

• RTLSDR-Airband version you are using (stable release number or branch/commit): 4.1.1

• make options used to build the program: cmake CMakeLists.txt -DNFM=ON -DPULSEAUDIO=ON -DMIRISDR=OFF -DSOAPYSDR=OFF -DRTLSDR=ON

• Hardware platform (eg. x86_64, Raspberry Pi v4): RPi v4

• Operating system name and version:
  Debian 11, kernel 6.1.21

What happened?
I wanted to record the sound of a radio at a frequency of 102.9 MHz with modulation NFM, but the script instead of the speaker's voice records incomprehensible noise, the frequency and modulation are exactly correct

What you expected to happen?
I expected in .mp3 file hear the speaker's voice

Steps to Reproduce
sudo rtl_airband -f -c rtl_airband.conf

Additional context
Add any other relevant information about the problem here.

Your rtl_airband.conf file
Remove passwords, server addresses and other private information.

devices: (
{
type = "rtlsdr";
index = 0;
gain = 38.6
centerfreq = 125.0
channels: (
{
freq = 124.0;
modulation = "am";
outputs: (
{
type = "file";
directory = "/home/rootmalina";
filename_template = "channel_1";
append = true;
}
);
},
{
freq = 102.9;
modulation = "nfm";
outputs: (
{
type = "file";
directory = "/home/rootmalina";
filename_template = "channel_2";
append = true;
}
);
},
{
freq = 129.5;
modulation = "am";
outputs: (
{
type = "file";
directory = "/home/rootmalina";
filename_template = "channel_3";
append = true;
}
);
},
{
freq = 133.1;
modulation = "am";
outputs: (
{
type = "file";
directory = "/home/rootmalina";
filename_template = "channel_4";
append = true;
}
);
},
{
freq = 139.3;
modulation = "am";
outputs: (
{
type = "file";
directory = "/home/rootmalina";
filename_template = "channel_5";
append = true;
}
);
},
{
freq = 124.45;
modulation = "am";
outputs: (
{
type = "file";
directory = "/home/rootmalina";
filename_template = "channel_6";
append = true;
}
);
},
{
freq = 130.75;
modulation = "am";
outputs: (
{
type = "file";
directory = "/home/rootmalina";
filename_template = "channel_7";
append = true;
}
);
}
);
}
);

[SullivanChrisJ]

102.9 MHz would be a commercial FM station, with a bandwidth of about 180 kHz. That isn't NFM (narrowband FM) which is more like 16 kHz.