In movies, the killer’s voice over the phone sounds bizarre and alien, which adds to the suspense. This is due to the frequency band limitations of phones and the effect of voice modulation. As the voice is converted into electrical signals, the original timbre and sound quality is altered, and horror movies in particular maximize this feature to immerse the audience. Recently, AI technology has also been used for investigative purposes, analyzing the unique characteristics of the voice to help catch criminals.
One of the most impressive aspects of a movie about a criminal is their voice. When the screen goes dark and a scared character picks up the phone, the killer’s bizarre voice instantly heightens the tension. In a similar way, phone voices in many movies play an important role in scaring the audience. In particular, the voice of a kidnapper coming over the phone line is particularly frightening. While many people may think that this is just a stylistic trick, there are real technical reasons why phone voices sound different from the original.
In real life, there is a difference between the voice you hear on a phone call and the voice you hear when you talk to a real person. This is due to the modulation that occurs when the phone converts the voice into an electrical signal and transmits it. The original voice undergoes various changes in sound quality, timbre, frequency range, etc. just by going through a mechanical process. This makes it difficult for law enforcement agencies to identify the perpetrator based on the voice on the phone. In particular, phone voices are often intentionally altered in movies to create a scary atmosphere.
Let’s take a look at how phones work and how voice modulation works. The basic principle of a telephone is to convert your voice into an electrical signal that is then transmitted to the other party. During this process, the voice signal is divided into two main stages. The first is when the microphone converts the sound into an electrical signal. The second is the transmission of that signal, which is then reproduced by the receiver through a speaker. The voice frequencies that are transmitted in a phone signal are limited to around 300 Hz to 3,400 Hz. The full frequency range of human speech is about 20 Hz to 20,000 Hz, and only a fraction of that is transmitted to the phone. As a result, a lot of the bass and treble parts of the human voice are lost.
This frequency band limitation is an important reason why the shooter’s voice sounds different. In movies and in real life, phone calls sound flatter, less toned, and higher pitches are emphasized due to this limited frequency band. In real life, voices on the phone sound shrill and unfamiliar, so crime movies often take advantage of this to make the criminal’s voice sound even more bizarre.
Also, when voice modulation technology is used in crime movies, certain sound effects are often added to increase the sense of fear. These sound effects are especially dramatic in scenes involving kidnappings or threatening phone calls. Typically, they emphasize the highs and lows at the same time, or add irregular electronic effects to make the audience feel the psychological tension of the caller. Adding tremors or echoes to the voice is another technique often used to create a frightening atmosphere.
Voice modulation isn’t just a cinematic technique, it also plays an important role in real-life criminal investigations. In cases involving threatening phone calls or unidentified individuals, law enforcement agencies use voice modulation and voice analysis to try to determine the identity of the perpetrator. Techniques include analyzing specific frequencies to identify unique features of a voice, or examining timbre to match it to a specific person. In recent years, advances in voice analysis using artificial intelligence (AI) have made it possible to analyze subtle features of a voice that were previously indistinguishable.
As such, phone voice modulation and sound effects are not just gimmicks, but have real-world implications. In movies, in particular, they are used dramatically to make the audience feel suspenseful based on the criminal’s voice alone. In real life, we also feel psychological pressure based on voice alone, which shows how important voice differences can be in criminal investigations involving phones.
