Voice Assistant

A voice assistant is a program you can talk to instead of typing. You say a sentence, and the device reacts: it plays music, tells you the weather, sets an alarm, or turns on the light. Well-known examples are Alexa from Amazon, Siri from Apple, and Google Assistant. They run on speakers, phones, TVs, and in cars. There is an important difference from a normal dictation function: dictation just writes down what you say, whereas a voice assistant tries to understand what you want to achieve and then acts on it.

Speech as a user interface

Speech is the fastest form of input humans know. We speak about three times faster than we type on a phone keyboard. That’s why voice assistants are especially handy wherever your hands are busy. While cooking, driving, or exercising, a screen just gets in the way.

For people with limited eyesight or fine motor skills, voice control is more than a convenience. It’s often what makes access to many devices possible at all. Older users, too, frequently find it easier to use speech than to navigate nested menus.

For companies, the voice assistant is also a gateway to the customer. Whoever asks which product should be ordered has a say in the sale. That’s precisely why Amazon, Google, and Apple spent years investing billions in these devices, often selling them below manufacturing cost. The second reason is trickier: every request reveals something about the user, and that data is valuable.

From sound wave to action

The process consists of four steps. First, the device listens for a wake word like “Alexa” or “Hey Siri.” This part runs directly on the device and is deliberately kept simple. Only after the wake word does the actual recording begin.

In the second step, the recording is converted into text. This technology is called speech recognition, and it matches sound waves to the most probable words. In the third step, a program interprets the intent behind the text. “Make it warmer” becomes a command to the heating system with a specific numeric value.

In the fourth step, the system responds. A speech synthesizer then turns text back into artificial speech. Part of the computing work usually happens on servers on the internet, not in the speaker itself. Newer assistants use large language models for this—AI systems that have learned from vast amounts of text how to continue phrasing. That’s why their answers sound more natural today, but they also make up more invented details.

Alexa, Siri, and customer service on the phone

In everyday life, you most often encounter voice assistants on smartphones and smart speakers. Car manufacturers build them in permanently so drivers don’t have to tap the navigation. TVs and remote controls often have a microphone for searching for movies.

A second, less popular variant can be heard on phone hotlines. There, voice dialog systems replace staff and ask about the customer’s issue. Behind this lies the same chain of speech recognition and intent interpretation, only with a narrow, fixed subject area.

Voice assistants tend to make the news for two reasons. First, data privacy: it repeatedly comes out that recordings of people were listened to in order to improve recognition. Second, the business model, because the devices earned less money than hoped. Since 2024, the industry has been rebuilding its assistants on AI language models and in some cases charges a subscription for it.