There're basiclly four tones in Mandarin Chinese / Putonghua. The 1st tone [ ˉ ] is high level, the 2nd tone [ˊ] is high rising level, the 3rd tone [ ˇ ] is the low dipping level, and the 4th tone [ˋ] is the high falling level.
The second tone(ˊ): High rising level, the pitch value is . When pronounce, the vocal cords is gradually tightening from neither loose nor tighten condition to "the most tight condition". The sound rose from neither low nor high to the highest.
The third tone( ˇ ): Low dipping level, the pitch value is . When pronounce, the vocal cords may be drawn to tight condition but little at the beginning, immediately relaxed and extended in duration slightly, and then rapidly tightened (but not drawn to "the most tight condition"). In the process, it is mainly in the bass voice of 1-2 degrees, and this is the basic features of the third tone. The duration of the sound of the third tone in the four tones of Mandarin is the longest.
The fourth tone(ˋ): High rising level, the pitch value is . the vocal cords is tight at the beginning till complete relaxation, the voice change from high to low. The duration of the sound of the fourth tone in the four tones of Mandarin is the shortest.
The neutral tone and the tone sandhi are special phenomenons in Chinese Putonghua. Neutral tone is normally pronounced short and light in special conditions and usually occurs on stressless syllable; thus 我们(wǒ mén, we) is said (wǒ men).
The tone sandhi is the occurence of allophonic and phonemic changes when tones come together; thus 很好(hěn hǎo, well) is said (hén hǎo).
Important!! most of chinese-learners have spoken the chinese putonghua in a strange intonation, it is because they have not caught hold of the tone and the tone sandhi.