Streaming Audio Quality and Lossless Music

What audio quality means

Sound is stored as a series of measurements of a wave, taken many times a second. How closely the stored version matches the original depends on two things: how the audio was captured and how it was compressed afterward.

Raw, uncompressed digital audio takes a lot of space. Compression exists to shrink it so that songs download quickly and use less data. There are two broad kinds of compression, and they differ in whether anything is thrown away.

Lossy and lossless

Lossy compression removes parts of the sound that, according to models of human hearing, are least likely to be noticed. MP3, AAC and Ogg Vorbis are common examples. The removal cannot be undone, so the file does not contain everything the original did. The smaller the file, the more is typically discarded.

Lossless compression shrinks the file without discarding anything, much like a zip file for sound. When decoded, it reproduces the original data exactly. FLAC and Apple’s ALAC are well-known lossless formats. Lossless files are generally larger than lossy ones, though typically smaller than uncompressed audio.

A third term worth knowing is uncompressed audio, such as WAV, which holds the full data without any shrinking.

The numbers that get quoted

Bitrate is the amount of data used per second of audio, usually in kilobits per second (kbps). Streaming services commonly use lossy bitrates in the range of roughly 96 to 320 kbps, depending on the service, the setting and the codec. Efficient codecs can sound better at a given bitrate than older ones, so the number alone does not decide quality.

CD quality uses a sample rate of 44.1 kHz and a bit depth of 16 bits, with two channels for stereo. Multiplying those, 44,100 samples per second times 16 bits times 2 channels gives 1,411,200 bits per second, or about 1,411 kbps. Lossless compression typically reduces this, often to somewhere around half, depending on the music.

Hi-res audio usually means higher sample rates or bit depths than CD, such as 96 kHz or 24 bits. The files are larger again. Many services label tiers using these terms, but exact definitions vary between companies.

Can you hear the difference?

This is the honest part: sometimes, but often not, and it depends on many factors.

• Modern lossy codecs at higher settings are designed to be hard to tell from the original in ordinary listening. Many people cannot reliably distinguish a high-quality lossy stream from lossless when tested blind, though individual results vary, and some listeners do notice differences with certain recordings.
• Low bitrates are easier to detect. At the low end, cymbals can sound smeared and dense passages can lose clarity.
• The recording matters. A well-made recording of acoustic music may show more difference than a heavily processed pop track.
• Your environment matters. On a bus or while exercising, background noise masks fine detail. A quiet room and good equipment give the best chance to hear differences.
• Your equipment matters. Basic speakers or earbuds may not reproduce the detail that lossless carries. A good pair of wired headphones or a decent speaker setup reveals more.
• Your hearing matters. Age and exposure to loud sounds affect what you can hear, especially at high frequencies.

Expectation also plays a role. People often report hearing improvements when they know they are listening to the more expensive option, which is why blind comparisons are more informative than casual impressions.

The Bluetooth bottleneck

Wireless listening is a frequent reason lossless does not help. Audio sent over Bluetooth is itself compressed using a Bluetooth codec, and the connection has limited capacity. Even if the streaming service provides a lossless file, a standard Bluetooth link will typically re-compress it before it reaches your ears. Some codecs and devices support higher quality, but both the phone and the headphones must support the same one. The basics of Bluetooth earbuds and what they can carry are covered separately. For lossless to make a difference, a wired connection or a compatible high-capacity wireless setup is usually needed.

Other weak links include the phone’s output, any equalizer or volume-levelling features, and the cheap cable or adapter at the end of the chain.

Data and storage costs

Higher quality uses more data. A lossless stream can use several times as much data per hour as a typical lossy one. If you stream on a mobile plan with a cap, or save songs for offline use, that adds up. Offline lossless libraries can take a lot of room, so keep an eye on how your phone storage is being used. Many apps let you set one quality for Wi-Fi and a lower one for mobile data.

A weak connection also matters. A lossless track needs a faster, steadier connection, and a stall in the middle of a song is more annoying than a small drop in quality. The same adaptation behind video, in which services switch quality as conditions change, applies to music, and the ideas are explained in the overview of how streaming and digital media work.

Practical advice

1. Try it yourself. Many services offer a trial. Listen to a familiar track at both settings, on your usual equipment, without looking at which is playing if you can.
2. Match the tier to your setup. If you mostly use Bluetooth earbuds on the move, a high-quality lossy setting is usually sensible.
3. Spend on the listening end first. Better headphones or speakers often make a bigger difference than a higher streaming tier.
4. Watch your data. Use lower quality on mobile data if you have a cap.
5. Check the claims. Terms like hi-res and studio quality are marketing labels. Look for the actual format, bit depth and sample rate.

Lossless is not a trick or a scam, and it is not magic either. For some listeners in the right conditions, it offers a small but real benefit, and for many others, it is not noticeable.