How can humans and aliens reliably communicate?

Question

Let's say that humanity has started a galactic empire, one of the things the embassy of Earth must do is communicate with a variety of alien species.

• The Vogavlüeans - The language of these subtropical hexapodal creatures consists of a variety of chirps and squeels.
• The Myrshakälans - The language of these bipedal, four armed aliens consists of hisses and voiceless breaths.
• The Bochahë - This species of deep sea merpeoples language consists of sonars and squeeks.
• The Triacyclicia - These 3-gendered anteater like creatures communicate with eachother using not sound but touch.
• The K'tathi - This collective consisness species' language consists of pheromones.
• The Seräphii - The Seräphii communicate using a strange language of click consonants.
• The Daleth - This flying nocturnal species relies on a system of chittering and echolocation in order to communicate

Obviously, the rules of probably say that it's extremely unlikely that these aliens would even be able to pronounce human sounds. How can the humans reliably communicate with the above aliens? How can the aliens reliably communicate with each other?

Answer 1

This problem can be overcome using abstract digital characters, essentially an alphabet much like ours, itemzed and encoded into codepoints similar to our own unicode. Since encoded characters abstract away the physical, sonic qualities of speech into semantic characters (‘letters’ in our language), they can be used as a universal format of communication. They are easy to learn; in fact you are reading this answer right now using abstract digital characters, all without hearing any auditory speech at all. And they are easy to transmit—we already know how to encode them into binary bits, essentially a glorified morse code, and we are quite good at this, see UTF-8 and associated technologies, which are extensible and allow for variable bit widths.

Since the characters themselves are abstracted away from the physical qualities of speech, each species can develop its own way of rendering and understanding them. For humans, we use technology known as fonts to convert the characters visually into representations called glyphs which can be read on paper or on screens. For humans without sight, we instead represent these characters as raised dots known as braille. Notice that the characters and their meaning are unchanged; only the representation is different. Other species could render abstract digital characters as any combination of scents, sounds, shapes, electrical mind signals, you name it.

Answer 2

If neither of the parties can emulate the other party's way of speech, by necessity, a translator is needed.

Unless bio-engineering advances enough, such a translator would need to me mechanical/electrical.

A better solution, which requires more cooperation by the other species, would be to create a language that can be spoken by everyone.

Since everyone can move and see (at least if your species make evolutionary sense), such a language would best be of a writable form. A broad language with symbols derived from pictures would probably be best to make sure it can be easily understood and learned by other species.

Another, more complex, language would be prepared for use when the "easy" language isn't enough, but would require at least some individuals of the other species to make considerable effort to learn it.

Answer 3

They can communicate using mathematics - By using prime numbers and patterns, you can show at least some knowledge of advanced mathematics. The book Prime Numbers and the search for Extraterrestrial Intelligence goes into this in more detail.

In fact, the movie Contact also uses math to communicate. Aliens, through the use of numbers, send blueprints to the humans, which helps them to build a communication device.

Having the technology to communicate with other races pretty much guarantees that the civilization(s) in question have access to advanced mathematics.