1) "Mandarin Chinese Pinyin Chart with Audio," Yabla, https://chinese.yabla.com/chinese-pinyin-chart.php (accessed 6 February 2019). This chart displays all the syllables in Mandarin Chinese. When you click on a syllable, you get a menu which lets you select which tone to hear the syllable pronounced in.

2) "Mandarin Chinese Pinyin Chart," DigMandarin, https://www.digmandarin.com/chinese-pinyin-chart (accessed 6 February 2019). Similar to the preceding, but with the syllables drawn out more (which makes them easier to hear, but is less faithful to actual speech).

3) "Say It Right," Chinesepod, https://chinesepod.com/tools/pronunciation (accessed 6 February 2019). This is a series of lessons explaining in detail pinyin pronunciation. If you have the patience, this is actually a good way to learn pronunciation.

4) Pleco Software, Pleco Chinese Dictionary, https://www.pleco.com/ (accessed 6 February 2019). The basic version of this app is available for both iOS and Android free of charge. It includes pronunciations (read in either a male or female voice) for each character, and provides a variety of ways to look up characters, including by Pinyin romanization or by the "radical" (explained in the next section). Best of all, you can just write a character with your finger on the screen to look it up. You can pay for various add-ons, including Kroll’s Student’s Dictionary of Classical and Medieval Chinese.