Hello!
I have a question. I am intending to record a rap song in Audacity, but I would like to ‘clean’ my voice, so it would sound a little bit similar to voices in rap songs.
I have a Phillips microphone.
Any suggestions?
This is the “announcer voice” thing. “I have a high squeaky voice and I want to sound like Don Pardo.” The tools that change pitch also mess with S and T sounds or make you sound all science fiction. Changing the quality of your voice isn’t one of the Audacity tools.
Try it. Effect > Change Pitch. As long as you don’t go too far, it can change things so you don’t quite sound like you. Good voice performers can sound like two or three different people with no help. A lot of voice performance is rhythm and annunciation, too. Hard to do that in software.
Ever recognize somebody through a really bad cellphone connection? That’s all rhythm. There’s no voice quality there at all.
Koz
If you are not getting a “clean” recording, it could be your mic, or the acoustics/soundproofing in your “studio”, or mic position, or the recording level, etc. If you don’t start with a good performance and a good recording, there’s only so much you can do in “post production”.
The pros have lots of tools & tricks, but it all starts with a good recording. For example, most movie soundtracks are re-recorded in the studio because it’s too difficult to get a good recording “on location”, and the tools to clean it up don’t exist in “real life”.
You can use the Equalizer effect to adjust frequency balance (without changing pitch). Boosting the 100 - 300Hz range should give your voice more bass.
Talking close into a directional mic (proximity effect) will also help with that “Don Pardo” male-announcer-voice effect. But if you get too close to the mic, you can also end-up “popping your Ps” (breath sounds called “plosives”.)
Another trick is to use dynamic compression (compressor effect, not related to file compression like MP3). Compression boosts the average/overal volume without boosting and clipping (distorting) the peaks. Pop & rap music generally uses lots of compression. If you’ve got a good voice and a good mic, compression might be the difference in your recording and the professional rap tracks you are listening to.
You can also try doubling your voice (recording two or more times and mixing), or you can search for an automatic double tracking effect or there are ways to create your own ADT effect involving a small time-shift, etc. A subtle chorus effect might help too.
I have a Phillips microphone.
What kind of mic is that? Regular “computer mics” are lousy and the mic inputs on most soundcards lousy too. 
Good mics are low impedance balanced and have an [u]XLR connector[/u] and require an audio interface (or a preamp connected to your computer’s line-in) or they have a USB connection (such as the [u]AT2020 USB[/u]). “Good” mics generally start around $100 USD. The most popular vocal mic in the world is the Shure SM58. You won’t anything as cheap as the SM58 used the much in pro recording studios, but it’s used on stage everywhere and the rumor is that Bono (U2) uses one in the studio.
Thank you for your answers!
Well I don’t have a made voice yet, but I am trying my best to improve it. Concerning microphone, it is a Karaoke companion from Philips (dynamic microphone, 27 mm diaphragm, 85-11.000 Hz frequency range, -74dB sensitivity, impedance 600 Ohm and so on)