There is not just one German language. There are three standard variations of German. (The links will bring you to the corresponding wikipedia articles in English and German):
These are three standardized languages that differ in some details of their standards.
To be a standard language means:
- It is taught in schools
- There are textbooks which describe this language
- It is used to write official documents like laws
- It is used by professional speakers in professional settings (i.e. in news programs on TV or radio)
None of these criteria is true for dialects, but they hold for all of the three standard variations of German. Please read the wikipedia articles if want detailed informations about differences between these three German languages.
You asked about pronunciation, and there are significant differences between these three languages. In the German wikipedia article about Austrian German you can find a section about Österreichische Aussprache und das Lautsystem ("Austrian pronunciation and sound system"), but pronunciation of Swiss Standard German differs even more from the two other variations.
But pronunciation is not a criterion for standardization. The main goal of standardization is written German, and the most standardized part of German language is orthography, which is identical for all three variations of German language, with one very important exception: The letter »ß« (called »Eszett« in German German but »scharfes S« in Austrian German) does not exist in Swiss German. Instead you use »ss« in Swiss German.
But there are also some minor differences which are induced by differences in pronunciation. For example the word »Geschoß/Geschoss« (floor of a building but also bullet from a gun): In German German the vowel o in Geschoss is pronounced short, while in Austrian German the o in Geschoß is pronounced long. But the rule for ß vs. ss says: After short vowels comes ss, after long vowels it must be ß, and so the difference in pronunciation finds its way into the highly uniformed orthography.
Two paragraphs above I said pronunciation is not a criterion for standardization. This is, because pronunciation is highly influenced by dialects. In its whole history German never has been just one language. It always has been a group of more or less similar dialects spoken by Germanic tribes in the center of Europe. There is a long history of aims to create a uniform German language, too long to tell here, but this process still has not come to an end.
I already mentioned High German dialects spoken in the south, in the high mountains of the alps (this is where the word "high" in "High German" comes from). This group of dialects can be divided further, and I think the biggest group of High German dialects is the group of Bavarian dialects. Some linguists count Bavarian as a distinct language because it is so different from Standard German (Wikipedia article about Bavarian language in Bavarian language).
95% of all residents of Austria speak Bavarian dialects, and this is why Austrian Standard German differs from German Standard German, and this also is the reason why the pronunciation of German is different in Austria. Some of the main characteristics of pronunciation of Bavarian dialects is the missing voiced s (written as [z] in IPA), and this is the reason why people from Austria and Bavaria always use the voiceless s (IPA symbol: [s]). We in Austria also don't make a difference in the pronunciation of »ä« and »e«. When a person from Austria in best Standard German says
Im Wald sind Bären.
There are bears in the forest.
Im Wald sind Beeren.
There are berries in the forest.
you will not hear any difference, but you will hear a clear difference when a person from Cologne, Hamburg, Berlin or Dresden says both sentences.
Also the process of Auslautverhärtung (Final-obstruent devoicing), which is made unconsciously by German native speakers from northern regions is produced much weaker from German native speakers from southern regions, and in many regions of Austria you won't hear it at all. And this has a big effect on the pronunciation of words that end in -ig like »König«, »selig«, »Honig« or »vierzig«
The standard pronunciation of König is [ˈkøːnɪk] with [k] at the end, as an effect of Auslautverhärtung. But in Austria you will hear [ˈkøːnɪg]. (This variation of pronunciation is not listed on the wiktionary page, but it is still used in Austria.) But for all words ending in -ig there is a second standard pronunciation, which many people believe to be the only one standard pronunciation. (But it isn't, there are two ways to pronounce it in German Standard German.) And in the case of König it is [ˈkøːnɪç], so its last two sounds are equal to the word ich [ɪç]. The funny part about this kind of pronunciation is, that you don't hear it very often in Austrian Standard German, but it still is used in dialects spoken in Austria. For example the word selig (German Standard German pronunciations: [ˈzeːlɪç], [ˈzeːlɪk]) is pronounced [ˈseːlɪg] in Austrian Standard German but [ˈsøːɫɪç] in Viennese Dialect.
Sorry for speaking so much about pronunciation of German language in Austria and in Bavarian dialects, but this is the region where I live, and so I know this variation very well. But there are also Low German dialects, spoken in the flat northern regions of Germany. Many linguists have also given Low German the status of a distinct language (Plattdeutsch or Niederdeutsch) and Wikipedia is also available in this language. (Wikipedia article about Low German, written in Low German) This language or group of dialects also has a big influence on the pronunciation of standard German in northern regions of Germany, but I'm sorry, I do not know very much about this language.
1Sorry, the English Wikipedia article German Standard German is very rudimentary and not worth to be listed together with the other articles.
2The German term Hochdeutsch is ambiguous. It can mean Standard German (Standarddeutsch) which is a standardized language but also High German (Hochdeutsche Dialekte) which is not standardized. It is a group of dialects spoken in Switzerland, Liechtenstein Austria, South Tyrol (with is a region in the north of Italy), and southern regions of Germany.